Inter prediction method and apparatus in video coding system

ABSTRACT

A video decoding method performed by a decoding apparatus includes the steps of: deriving control points (CP) for a current block; acquiring movement vectors for the CPs; deriving a sample unit movement vector in the current block on the basis of the acquired movement vectors; and deriving a prediction sample for the current block on the basis of the sample unit movement vector. According to the present invention, it is possible to effectively perform, through sample unit motion vectors, inter-prediction not only in a case where an image in the current block is plane-shifted but also in a case where there are various image distortions.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.17/348,204, filed on Jun. 15, 2021, which is a continuation of U.S.application Ser. No. 16/773,958, filed on Jan. 27, 2020, now U.S. Pat.No. 11,122,290, which is a continuation of U.S. application Ser. No.15/751,077, filed on Feb. 7, 2018, now U.S. Pat. No. 10,582,215, whichis a National Stage application under 35 U.S.C. § 371 of InternationalApplication No. PCT/KR2016/007734, filed Jul. 15, 2016, which claims thebenefit of U.S. Provisional Application No. 62/202,182, filed on Aug. 7,2015. The disclosures of the prior applications are incorporated byreference in their entirety.

TECHNICAL FIELD

The present invention relates to a video coding technology and, moreparticularly, to an inter-prediction method and apparatus in a videocoding system,

BACKGROUND

Demand for high-resolution, high-quality images such as HD (HighDefinition) images and UHD (Ultra High Definition) images has beenincreasing in various fields. As the image data has high resolution andhigh quality, the amount of information or bits to be transmittedincreases relative to the legacy image data. Therefore, when image datais transmitted using a medium such as a conventional wired/wirelessbroadband line or image data is stored using an existing storage medium,the transmission cost and the storage cost thereof are increased.

Accordingly, there is a need for a highly efficient image compressiontechnique for effectively transmitting, storing, and reproducinginformation of high resolution and high quality images.

SUMMARY

The present invention provides a method and a device for enhancing imagecoding efficiency.

Another technical purpose of the present invention is to provide anaffine motion model based inter-prediction method and device.

Another technical purpose of the present invention is to provide amethod and device for performing sample unit motion vector basedinter-prediction.

Another technical purpose of the present invention is to provide amethod and device for deriving a sample unit motion vector based on amotion vector of control points for the current block.

Another technical purpose of the present invention is to provide amethod and device for deriving a motion vector regarding control pointsof a current block as a non-square block based on a sample of aneighboring block.

Another technical purpose of the present invention is to provide amethod and device for deriving a motion vector regarding a control pointof a current block based on a motion vector regarding a control point ofa previously decoded neighboring block.

In an aspect, a video decoding method performed by a decoding device isprovided. The decoding method includes: deriving control points (CPs)for a current block; obtaining motion vectors for the CPs; deriving asample unit motion vector in the current block on the basis of theobtained motion vectors; and deriving a prediction sample for thecurrent block on the basis of the sample unit motion vector.

In another aspect, a decoding device performing video decoding isprovided. The decoding device includes: a decoding unit obtainingprediction mode information regarding a current block from a bit stream;a prediction unit deriving control points (CPs) regarding the currentblock, obtaining motion vectors regarding the CPs, deriving a sampleunit motion vector in the current block based on the obtained motionvectors, and deriving a prediction sample regarding the current blockbased on the sample unit motion vector; and an adder generating areconstructed sample based on the prediction sample.

In another aspect, a video encoding method performed by an encodingdevice is provided. The video encoding method includes: driving controlpoints (CPs) regarding a current block; obtaining motion vectorsregarding the CPs; deriving a sample unit motion vector in the currentblock based on the obtained motion vectors; generating a predictionsample regarding the current block based on the sample unit motionvector; and encoding prediction mode information regarding the currentblock and outputting the encoded prediction mode information.

In another aspect, an encoding device performing video encoding isprovided. The encoding device includes: a prediction unit determining aprediction mode regarding a current block, deriving control points (CPs)regarding the current block, obtaining motion vectors regarding the CPs,deriving a sample unit motion vector in the current block based on theobtained. motion vectors, and generating a prediction sample regardingthe current block based on the sample unit motion vector; and anencoding unit encoding prediction mode information regarding the currentblock and outputting the encoded prediction mode information.

According to the present invention, more accurate sample-based motionvectors for the current block may be derived and thus theinter-prediction efficiency may be significantly increased.

According to the present invention, motion vectors for samples in thecurrent block may be efficiently derived based on the motion vectors ofthe control points for the rent block.

According to the present invention, motion vectors of control points fora current block may be derived based on motion vectors of control pointsof a previously decoded neighboring block, without additionAytransmitting information regarding the motion vectors of the controlpoints for the current block. Accordingly, an amount of data for themotion vectors of the control points may be eliminated or reduced, andoverall coding efficiency may be improved.

According to the present invention, inter-prediction may be effectivelyperformed through sample unit motion vectors even in case where an imagein the current block is rotated, zoomed in, zoomed out, or deformed toparallelogram, as well as in case where the image of the current blockis plane-shifted. Accordingly, an amount of data for a residual signalfor the current block may be eliminated or reduced, and overall codingefficiency may be improved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram schematically illustrating a video encodingdevice according to an embodiment of the invention.

FIG. 2 is a block diagram schematically illustrating a video decodingdevice according to an embodiment of the invention.

FIG. 3 is a view illustrating a configuration in which a prediction isgenerated in inter-prediction to which a translational motion model isapplied.

FIG. 4 is a view illustrating a configuration in which a predictionblock is generated in inter-prediction to which an affine motion modelis applied.

FIG. 5 is a view illustrating a state in whith a prediction block isgenerated and a motion vector in inter-prediction to which the affinemotion model is applied.

FIG. 6 is a view illustrating CPs of a PU partitioned from a CU based ona partitioning type 2N×2N.

FIG. 7 is a view illustrating CPs of PUs partitioned from a CU based ona partitioning type N×2N.

FIG. 8 is a view illustrating CPs of PUs partitioned from a CU based ona partitioning type 2N×N.

FIG. 9 is a view illustrating CPs of asymmetric PUs.

FIG. 10 is a view illustrating motion information prediction candidatesof CPs of a PU to the partitioning type 2N×2N is applied.

FIG. 11 illustrates an example of motion information predictioncandidates of CPs of a PU to which a partitioning type 2N×N is applied.

FIG. 12 is a view illustrating a configuration in which predictioncandidates of CPs of a PU to which the partitioning type 2N×N is appliedare limited to two prediction candidates.

FIG. 13 is a view illustrating motion information prediction candidatesof CPs of a PU to which the partitioning type N×2N is applied.

FIG. 14 is a view illustrating a configuration in which predictioncandidates of the CPs of a PU to which the partitioning type N×2N isapplied are limited to two prediction candidates.

FIGS. 15A to 15D are views illustrating motion information predictioncandidates of CPs of asymmetric PUs.

FIG. 16 is a view illustrating a configuration in which predictioncandidates of CPs of asymmetric PUs are limited to two predictioncandidates.

FIG. 17 is a view illustrating a PU including a CP for which motioninformation coding is required and a CP for which motion informationcoding is not required.

FIG. 18 is a view illustrating a PU including CPs for which motioninformation coding is not required.

FIG. 19 is a view schematically illustrating a video encoding method byan encoding device according to the present invention.

FIG. 20 is a view schematically illustrating a video decoding method bya decoding device according to the present invention.

DETAILED DESCRIPTION

The present invention may be modified in various forms, and specificembodiments thereof will be described and illustrated in the drawings.However, the embodiments are not intended for limiting the invention.The terms used in the following description are used to merely describespecific embodiments, but are not intended to limit the invention. Anexpression of a singular number includes an expression of the pluralnumber, so long as it is clearly read differently.

The terms such as “include” and “have” are intended to indicate thatfeatures, numbers, steps, operations, elements, components, orcombinations thereof used in the following description exist and itshould be thus understood that the possibility of existence or additionof one or more different features, numbers, steps, operations, elements,components, or combinations thereof is not excluded.

On the other hand, elements in the drawings described in the inventionare independently drawn for the purpose of convenience for explanationof different specific functions in an image encoding/decoding device anddoes not mean that the elements are embodied by independent hardware orindependent software. For example, two or more elements of the elementsmay be combined to form a single element, or one element may be dividedinto plural elements. The embodiments in which the elements are combinedand/or divided belong to the invention without departing from theconcept of the invention.

Hereinafter, exemplary embodiments of the invention will be described indetail with reference to the accompanying drawings.

FIG. 1 is a block diagram schematically illustrating a video encodingdevice according td an embodiment of the invention.

Referring to FIG. 1 , a video encoding device 100 includes a picturepartitioning module 105, a prediction module 110, a transform module120, a quantization module 125, a rearrangement module 130, an entropyencoding module 135, a dequantization module 140, an inverse transformmodule 145, a filtering module 155, and memory 160.

The picture partitioning module 105 may be configured to split the inputpicture into at least one processing unit block. In this connection, ablock as a processing unit may be a prediction unit PU, a transform unitTU, or a coding unit CU. The picture may be composed of a plurality ofcoding tree unit CTUs. Each CTU may be split into CUs as a quad treestructure. The CU may be split into CUs having a deeper depth as aquad-tree structures. The PU and TU may be obtained from the CU. Forexample, the PU may be partitioned from a CU into a symmetric orasymmetric square structure. Further, the TU may be split into a quadtree structure from the CU, The CTU may correspond to a coding treeblock CTB the CU may correspond to a coding block CB, the PU maycorrespond to a prediction block PB and the TU may correspond to atransform block TB.

The prediction module 110 includes an inter-prediction unit thatperforms an inter-prediction process and an intra prediction unit thatperforms an intra prediction process, as will be described later. Theprediction module 110 performs a prediction process on the processingunits of a picture divided by the picture partitioning module 105 tocreate a prediction block including a predicted sample or a predictedsample array. In the prediction module 110, the processing unit of apicture may be a CU, a TU, or a PU. The prediction module 110 maydetermine whether the prediction performed on the correspondingprocessing unit is an inter-prediction or an intra prediction, and maydetermine specific details for example, a prediction mode of theprediction methods. The processing unit subjected to the predictionprocess may be different from the processing unit of which theprediction method and the specific details are determined. For example,the prediction method and the prediction mode may be determined in theunits of PU and the prediction process may be performed in the units ofTU.

In the inter-prediction, a prediction process may be performed on thebasis of information on at least one of a previous picture and/or asubsequent picture of a current picture to create a prediction block. Inthe intra prediction, a prediction process may be performed on the basisof pixel information of a current picture to create a prediction block.

As an inter-prediction method, a skip mode, a merge mode, and AdvancedMotion Vector Prediction (AMVP) may be used. In inter-prediction, areference picture may be selected for the PU and a reference blockcorresponding to the PU may be selected. The reference block may beselected on an integer pixel (or sample) or fractional pixel (or sample)basis. Then, a prediction block is generated in which the residualsignal with respect to the PU is minimized and the motion vectormagnitude is also minimized. Pixels, pels, and samples may be usedinterchangeably herein.

A prediction block may be generated as an integer pixel unit, or as afractional pixel unit such as a ½ pixel unit or a ¼ pixel unit. In thisconnection, a motion vector may also be expressed as a fractional pixelunit.

Information such as the index of the reference picture selected via theinter-prediction, the motion vector difference MDV, the motion vectorpredictor MVP, residual signal, etc., may be entropy encoded and thentransmitted to the decoding device. When the skip mode is applied, theprediction block. may be used as a reconstruction block, so that theresidual may not be generated, transformed, quantized, or transmitted.

When the intra prediction is performed, the prediction mode may bedetermined in the unit of PU and the prediction process may be performedin the unit of PU. Alternatively, the prediction mode may be determinedin the unit of PU and the inter-prediction may be performed in the unitof TU.

The prediction modes in the intra prediction may include 33 directionalprediction modes and at least two non-directional modes, as an example.The non-directional modes may include a DC prediction mode and a planarmode.

In the intra prediction, a prediction block may be configured after afilter is applied to a reference sample. At this time, it may bedetermined whether a filter should be applied to a reference sampledepending on the intra prediction mode and/or the size of a currentblock.

Residual values (a residual block or a residual signal) between theconstructed prediction block and the original block are input to thetransform module 120. The prediction mode information, the motion vectorinformation, and the like used for the prediction are encoded along withthe residual values by the entropy encoding module 135 and aretransmitted to the decoding device.

The transform module 120 performs a transform process on the residualblock in the unit of TUs and generates transform coefficients.

A transform block is a rectangular block of samples and is a block towhich the same transform is applied. The transform block may be a TU andmay have a quad-tree structure.

The transform module 120 may perform a transform process depending onthe prediction mode applied to a residual block and the size of theblock.

For example, when intra prediction is applied to a residual block andthe residual block has an 4×4 array, the residual block is transformedusing discrete sine transform DST. Otherwise, the residual block may hetransformed using discrete cosine transform DCT.

The transform module 120 may construct a transform block of transformcoefficients through the transform.

The quantization module 125 may quantize the residual values, that is,transform coefficients, transformed by the transform module 120 and maycreate quantization coefficients. The values calculated by thequantization module 125 may be supplied to the dequantization module 140and the rearrangement module 130.

The rearrangement module 130 may rearrange the transform coefficientssupplied from the quantization module 125. By rearranging thequantization coefficients, it is possible to enhance the encodingefficiency in the entropy encoding module 135.

The rearrangement module 130 may rearrange the quantized transformcoefficients in the form of a two-dimensional block to the form of aone-dimensional vector through the use of a coefficient scanning method.

The entropy encoding module 135 may be configured to entropy code thesymbol according to a probability distribution based on the quantizedtransform values rearranged by the rearrangement module 130 or theencoding parameter value calculated during the encoding process, etc.and then to output a bit stream. The entropy encoding method is a methodof receiving a symbol having various values and expressing the symbol asa binary string that may be decoded while removing statisticalredundancy thereof.

In this connection, the symbol means the to-be encoded/decoded syntaxelement, coding parameter, residual signal value and so on. The encodingparameter is required for encoding and decoding. The encoding parametermay contain information that may be inferred during encoding ordecoding, as well as information encoded in an encoding device andpassed to a decoding device like the syntax element. The encodingparameter is the information needed to encode or decode the image. Theencoding parameter may include statistics or values such as for example,the intra/inter-prediction mode, movement/motion vector, referencepicture index, coding block pattern, residual signal presence orabsence, transform coefficient, quantized transform coefficient,quantization parameter, block size, block partitioning information, etc.Further, the residual signal may mean a difference between an originalsignal and a prediction signal. Further, the difference between theoriginal signal and the prediction signal may be transformed to definethe residual signal, or the difference between the original signal andthe prediction signal may be transformed and quantized to define theresidual signal. The residual signal may be called the residual block inthe block unit, and may be called the residual samples in the sampleunit.

When the entropy encoding is applied, the symbols may be expressed sothat a small number of bits are allocated to a symbol having a highprobability of occurrence, and a large number of bits are allocated to asymbol having a low probability of occurrence. This may reduce the sizeof the bit string for the to-be-encoded symbols. Therefore, thecompression performance of image encoding may be increased via theentropy encoding.

Encoding schemes such as exponential Golomb, Context-Adaptive VariableLength Coding (CAVLC), and Context-Adaptive Binary Arithmetic Coding(CABAC) may be used for the entropy encoding. For example, the entropyencoding module 135 may store therein a table: for performing entropyencoding, such as a variable length coding/code (VLC) table. The entropyencoding module 135 may perform entropy encoding using the stored VLCtable. Further, the entropy encoding module 135 derives a binarizationmethod of a corresponding symbol and a probability model of acorresponding symbol/bin, and then performs entropy encoding using thederived binarization method or probability model.

The entropy encoding module 135 may give a predetermined change to aparameter set or syntaxes to be transmitted, if necessary.

The dequantization module 140 dequantizes the values transformcoefficients quantized by the quantization module 125. The inversetransform module 145 inversely transforms the values dequantized by thedequantization module 140.

The residual value or residual samples or residual samples arraygenerated by the dequantization module 140 and the inverse transformmodule 145, and the prediction block predicted by the prediction module110 may be combined to form a reconstructed block including areconstructed sample or a reconstructed sample array.

In FIG. 1 , a residual block and a prediction block are added to createa reconstructed block by an adder. At this time, the adder may beconsidered as a particular unit reconstructed block creating unit thatgenerates a reconstructed block.

The filtering module 155 applies a deblocking filter, an ALF AdaptiveLoop an SAO Sample Adaptive Offset to the reconstructed picture.

The deblocking filter removes a block distortion generated at theboundary between blocks in the reconstructed picture. The ALF performs afiltering process on the basis of the result values of the comparison ofthe original picture with the reconstructed picture of which the blocksare filtered by the deblocking filter. The ALF may be applied only whenhigh efficiency is necessary. The SAO reconstructs offset differencesbetween the residual blocks having the deblocking filter applied theretoand the original picture and is applied in the form of a band offset, anedge offset, or the like.

The memory 160 may store the reconstructed block or picture calculatedby the filtering module 155. The reconstructed block or picture storedin the memory 160 may be supplied to the prediction module 110 thatperforms the inter-prediction.

FIG. 2 is a block diagram schematically illustrating a video decodingdevice according to an embodiment of the invention. Referring to FIG. 2, a video decoding device 200 may include an entropy decoding module210, a rearrangement module 215, a dequantization module 220, an inversetransform module 225, a prediction module 230, a filtering module 235,and memory 240.

When a video bit stream is input from the video encoding device, theinput bit stream may be decoded on the basis of the order in which videoinformation is processed by the video encoding device.

The entropy decoding module 210 may entropy-decode the input bit streamaccording to a probability distribution to generate symbols in aquantized coefficient form. The entropy decoding method is a method ofreceiving a sequence of binary numbers and generating each of thesymbols using the sequence. The entropy decoding method is similar tothe entropy encoding method described above,

For example, when a Variable Length Coding VLC (hereinafter referred toas ‘VLC’) such as CAVLC is used to perform entropy encoding in a videoencoding device, the entropy decoding module 210 may perform decodingusing the same VLC table as the encoding device used in the encodingdevice. Further, when CABAC is used to perform entropy encoding in avideo encoding device, the entropy decoding module 210 may perform theentropy decoding using CABAL

More specifically, the CABAC entropy decoding method may includereceiving a bin corresponding to each syntax element in a bit stream,determining a context model using to-be-decoded syntax elementinformation, decoding information of a neighboring block and ato-be-decoded block, or information of a symbol/bin decoded in aprevious step, and predicting a probability of occurrence of a binaccording to the determined context model and thus performing arithmeticdecoding of the bin to generate a symbol corresponding to a value ofeach syntax element. in this connection, after determining the contextmodel, the CABAC entropy decoding method may further include a step ofupdating the context model using the information of the decodedsymbol/bin to determine a context model of the next symbol/bin.

Information for constructing a predicted block out of the informationdecoded by the entropy decoding module 210 may be supplied to theprediction module 230, and the residual values, that is, the quantizedtransform coefficients, entropy-decoded by the entropy decoding module210 may be input to the rearrangement module 215,

The rearrangement module 215 may rearrange the bit stream information,that is, the quantized transform coefficients, entropy-decoded by theentropy decoding module 210 on the basis of the rearrangement method inthe video encoding device.

The rearrangement module 215 may reconstruct and rearrange thecoefficients expressed in the form of a one-dimensional vector intocoefficients in the form of a two-dimensional block.

The rearrangement module 215 may scan the coefficients on the basis ofthe prediction mode applied to the current block transform block and thesize of the transform block and may create an array of coefficientsquantized transform coefficients in the form of a two-dimensional block.

The dequantization module 220 may perform dequantization on the basis ofthe quantization parameters supplied from the video encoding device andthe coefficient values of the rearranged block.

The inverse transform module 225 may perform the inverse DCT and/orinverse DST of the DCI and/or DST, which has been performed by thetransform module of the video encoding device, on the quantizationresult from the video encoding device.

The inverse transform may be performed on the basis of a transfer unitor a partition unit of a picture determined by the video encodingdevice. The transform module of the video encoding device mayselectively perform the DCT and/or DST depending on plural informationpieces such as the prediction method, the size of a current block, andthe prediction direction, and the inverse transform module 225 of thevideo decoding device may perform the inverse transform on the basis ofthe transform information on the transform performed by the transformmodule of the video encoding device.

The prediction module 230 generates a prediction block including apredicted sample or a predicted sample array based on the predictionblock generation-related information provided by the entropy decodingmodule 210 and the previously decoded block and/or picture informationprovided from the memory 240.

If the prediction mode for the current PU is the intra prediction mode,the prediction module 230 may perform the intra prediction to generate aprediction block based on pixel information in the current picture.

If the prediction mode for the current PU is the inter-prediction mode,the prediction module 230 may be configured to perform inter-predictionon a current PU based on information included in at least one picture ofa previous picture or a subsequent picture to the current picture. Inthis connection, information about the motion information necessary forinter-prediction of the current PU provided in the video encodingdevice, such as motion vector and reference picture index may be deducedvia checking the skip flag and merge flag received from the encodingdevice.

The prediction module 230 may generate a prediction block such that theresidual signal relative to the current block is minimized and themotion vector size is minimized when inter-prediction is performed onthe current picture.

On the other hand, the motion information derivation method may bechanged according to the prediction mode of the current block. Theprediction mode applied to inter-prediction may include an Advanced.Motion Vector Prediction (AMVP) mode, a merge mode, and the like.

For example, when a merge mode is applied, the encoding device and thedecoding device may generate a merge candidate list using the motionvector of the reconstructed spatial neighboring block and/or the motionvector corresponding to the Col block which is a temporally neighboringblock. In the merge mode, the motion vector of the candidate blockselected in the merge candidate list is used as the motion vector of thecurrent block. The encoding device may transmit a merge index indicatinga candidate block having an optimal motion vector selected from thecandidate blocks included in the merge candidate list to the decodingdevice. In this case, the decoding device may derive the motion vectorof the current block using the merge index.

In another example, when the AMVP (Advanced Motion Vector Prediction)mode is applied, the encoding device and decoding device generate amotion vector predictor candidate list using a motion vector of areconstructed spatial neighboring block and/or a motion vectorcorresponding to a Col block as a temporal neighboring block. That is,the motion vector of the reconstructed spatial neighboring block and/orthe motion vector corresponding to the Col block as a temporalneighboring block may be used as a motion vector candidate. The encodingdevice may transmit to the decoding device a prediction motion vectorindex indicating the optimal motion vector selected from among themotion vector candidates included in the motion vector predictorcandidate list. In this connection, the decoding device may select theprediction motion vector for the current block from the motion vectorcandidates included in the motion vector candidate list using the motionvector index.

The encoding device may obtain the motion vector difference MVD betweenthe motion vector for the current block and the motion vector predictor(MVP), encode the MVD, and transmit the encoded MVD to the decodingdevice. That is, the MVD may be a value obtained by subtracting themotion vector predictor (MVP) from the motion vector (MV) for thecurrent block. In this connection, the decoding device may decode thereceived motion vector difference, and. derive the motion vector for thecurrent block via addition between the decoded motion vector differenceand the motion vector predictor.

Further, the encoding device may transmit a reference picture indexindicating a reference picture to the decoding device.

The prediction module 230 of the decoding device may predict the motionvector of the current block using the motion information of theneighboring block and derive the motion vector of the current blockusing the residual received from the encoding device. The decodingdevice may generate predicted sample (or predicted sample array) for thecurrent block based on the derived motion vector and the referencepicture index information received from the encoding device.

The decoding device may generate reconstructed samples (or reconstructedsamples array) by adding predicted sample (or predicted sample array)and residual samples as obtained from transform coefficients sent fromthe encoding device to each other. Based on these reconstructed.samples, reconstructed blocks and reconstructed pictures may begenerated.

In the above-described AMVP and merge modes, motion information of thereconstructed neighboring block and/or motion information of the Colblock may be used to derive motion information of the current block.

In the skip mode, which is one of the other modes used for inter-pictureprediction, neighboring block information may be used for the currentblock as it is. Therefore, in the case of skip mode, the encoding devicedoes not transmit syntax information such as the residual to thedecoding device in addition to information indicating which block'smotion information to use as the motion information for the currentblock.

The reconstructed block may be generated using the prediction blockgenerated by the prediction module 230 and the residual block providedby the inverse-transform module 225. FIG. 2 illustrates that using theadder, the prediction block and the residual block are combined togenerate the reconstructed block. In this connection, the adder may beviewed as a separate module (a reconstructed block generation module)that is configured to generate the reconstructed block. In thisconnection, the reconstructed block includes a reconstructed samples ora reconstructed samples array as described above; the prediction blockincludes a predicted sample or a predicted sample array; the residualblock may include a residual samples or a residual samples array.Therefore, the reconstructed samples or the reconstructed samples arraymay be considered to be generated by combining the correspondingpredicted sample or predicted sample array with the correspondingresidual samples or residual samples array.

When the skip mode is used for a block, the residual signal may not betransmitted and the predicted block may be used as a reconstructedblock.

The reconstructed block and/or picture may be supplied to the filteringmodule 235. The filtering module 235 may perform a deblocking filteringoperation, an SAO operation, and/or an ALF operation on thereconstructed block and/or picture.

The memory 240 may store the reconstructed picture or block for use as areference picture or a reference block and may supply the reconstructedpicture to an output unit.

The elements that is directly related to decoding images among theentropy decoding module 210, the rearrangement module 215, thedequantization module 220, the inverse transform module 225, theprediction module 230, the filtering module 235 and the memory 240 whichare included in the decoding device 200, for example, the entropydecoding module 210, the rearrangement module 215, the dequantizationmodule 220, the inverse transform module 225, the prediction module 230,the filtering module 235, and so on may be expressed as a decoder or adecoding module that is distinguished from other elements.

In addition, the decoding device 200 may further include a parsingmodule not illustrated. in the drawing that parses information relatedto the encoded images included in a bit stream. The parsing module mayinclude the entropy decoding module 210, and may be included in theentropy decoding module 210. Such a parsing module may also beimplemented as an element of the decoding module.

Inter-prediction may be performed on a current block in consideration ofmotion of a target object or an image between pictures. However, theexisting inter-prediction method is performed based on method ofcompensating for a translational motion (translational motion model).The translational motion model may be referred to as a block matchingmethod because inter-prediction is performed by deriving a referenceblock matched to the current block based on one motion vector. That is,in the method applied to the existing inter-prediction and thetranslational motion model, all samples of a prediction unit (IDU) havethe same motion information.

FIG. 3 is a view illustrating a way in which a prediction block isgenerated from inter-prediction to which the translational motion modelis applied.

Referring to FIG. 3 , since all the samples of a PU have the same motioninformation, prediction and compensation are performed in a limitedform. In detail, according to the translational motion model, a regionhaving the same shape and size as those of a prediction block within areference picture is designated as a prediction reference block using amotion vector MV_(x) in the x-axis direction and a motion vector MV_(y)in the y-axis direction, motion parameters for one motion vector inunits of PU, and samples within the reference block are used asprediction samples for the prediction block. However, application of thetranslational motion model has a limitation in that predictionefficiency is degraded over deformation such as enlargement, reduction,rotation, and the like, of an image. According to the present invention,it is possible to modify the process in which the same motioninformation is transmitted and derived in units of the existing PU, sothat the samples in the PU may have different motion information. Aprediction model according to the present invention may be referred toas a 2-dimensional affine transform method or an affine motion model.Inter-prediction using the affine motion model may be the same as thatillustrated in FIG. 4 .

FIG. 4 illustrates an example in which a prediction block is generatedin inter-prediction using an affine motion model. Hereinafter, thecurrent block may correspond to the PU.

Referring to FIG. 4 , x and y represent an x-coordinate and ay-coordinate of each sample in the current block, respectively. x′ andy′ represent an x-coordinate and a y-coordinate of a correspondingsample in a reference picture corresponding to x and y, respectively. Inthis case, a region including the samples at a sample position pointedto by (x′,y′) may be referred to as a reference block or a referenceregion. In this case, the reference block may correspond to a regionincluding an image transformed according to rotational deformation,shape deformation, size deformation such as zoom-in or zoom-out, etc.regarding an image within the current block. Therefore, a size and ashape of the reference block may be different from those of the currentblock. A specific method of deriving a motion vector which is differentor unique for each of the samples in the current block illustrated inFIG. 4 is illustrated in FIG. 5 .

FIG. 5 is a view illustrating a state in which a prediction block isgenerated and a motion vector in inter-prediction using an affine motionmodel. Referring to FIG. 5 , a formula for deriving a motion vector whenthe affine motion model is applied is shown. The motion vector may bederived based on the following equation.

(V _(x) , V _(y))≤(x−x′, y−y′)V _(x)=(1−a)x−by−e

V _(y=−cx)+((1−d)y−f   [Equation 1]

Here, v_(x) represents an x component of a sample unit motion vector ofa (x, y) coordinate sample in the current block, and v_(y) represents ay component of the sample unit motion vector of the (x, y) coordinatesample in the current block. That is, (v_(x), v_(y)) is the sample unitmotion vector for the (x, y) coordinate sample. Here, a, b, c, d, e, andf denote parameters of an equation for deriving the sample unit motionvector (motion information) of the (x, y) coordinates from controlpoints (CPs) of the current block. The CP may be expressed as a steeredpixel. The parameters may he derived from motion information of the CPsof each PU transmitted in units of PU. The equation for deriving thesample unit motion vector derived from the motion information of the CPsmay be applied to each sample of each PU or may be derived to a positionof a predicted sample in a reference image according to relativepositions of the x and y axes of each PU sample. The sample unit motionvector may be derived to be different depending on a size of a PUaccording to partitioning applied to a coding unit (CU), asymmetric orsymmetric type, a partition II), and the like. A specific embodimentthereof will be described with reference to FIGS. 6 to 16 .

FIG. 6 a view illustrating CPs of a PU partitioned from a CU based on apartitioning type 2N×2N.

As illustrated in Equation (1) above, the parameters of the equation forderiving the sample unit motion vector may be derived as differentvalues based on the motion vectors of the CPs of the current block. TheCPs may be three CPs. The CPs may use motion information of CPs atdifferent positions according to a shape of the PU.

Referring to FIG. 6 , a method in a PU partitioned from a CU based on apartitioning type 2N×2N for an equation for deriving the sample unitmotion vector is shown. For example, a motion Vector of a top-leftsample in the PU may be referred to as V₀. In addition, using samples ofneighboring blocks adjacent to the PU, motion vectors of each CP may beV₁ and V₂. That is, when a width and a height of the PU are S andcoordinates of a top-left sample position of the PU is (xp, yp),coordinates of CP0, among the CPs, may be set to (xp, yp), coordinatesof CP1 may be set to (xp+S, yp), and coordinates of CP2 may be set to(xp, yp+S). The motion vector of CP0 may be set to V₀, the motion vectorof CP1 may be set to V₁, and the motion vector of CP2 may be V₂. Thesample unit motion vector may be derived using the motion vectors of theCPs. The sample unit motion vector may be derived based on the followingequation.

$\begin{matrix}\begin{matrix}{V_{x} = {{\frac{V_{{x}_{1}} - V_{{x}_{0}}}{S}x} + {\frac{V_{{x}_{2}} - V_{{x}_{0}}}{S}y} + V_{{x}_{0}}}}\end{matrix} & \left\lbrack {{Equation}2} \right\rbrack\end{matrix}$$V_{y} = {{\frac{V_{{y}_{1}} - V_{{y}_{0}}}{S}x} + {\frac{V_{{y}_{2}} - V_{{y}_{0}}}{S}y} + V_{{y}_{0}}}$

Here, V_(x) and V_(y) represent an x component and a y component of amotion vector for a sample of the (x, y) coordinates in the currentblock, respectively, Vx₀ and Vy₀ represent an x component and a ycomponent of a motion vector V₀ for CP0, Vx₁ and Vy₁ represent an xcomponent and a y component of the motion vector V₁ for CP1, and Vx₂ andVy₂ represent an x component and a y component of the motion vector V₂for CP2, respectively. According to the equation for deriving the sampleunit motion vector as in Equation 2, a motion vector may be derivedbased on a relative position in the PU for each sample of the PUpartitioned from the CU based on the partitioning type 2N×2N.

FIG. 7 illustrates CPs of PUs partitioned from a CU based on thepartitioning type N×2N. Referring to FIG. 7 , a process of deriving amotion vector of PUs partitioned from the CU based on the partitioningtype N×2N is shown. An equation for deriving a sample unit motion vectorin the PU may be derived by the same method as that of the case of theaforementioned partitioning type 2N×2N. In the process of deriving theequation, a width value corresponding to the shape of the PU may beused. In order to derive the sample unit motion vector, three CPs may bederived and the positions of the CPs may be adjusted as illustrated inFIG. 7 . That is, when a width and a height of the PU are S/2 and S,respectively, and coordinates of the top-left sample position of the PUis (xp, yp), coordinates of CP0, among the CPs, are (xp, yp),coordinates of CP1 may b (xp+S/2, yp), and coordinates of CP2 may be(xp, yp+S). The sample unit motion vector may be derived based on thefollowing equation.

$\begin{matrix}{V_{x} = {{\frac{2\left( {V_{{x}_{1}} - V_{{x}_{0}}} \right)}{S}x} + {\frac{V_{{x}_{2}} - V_{{x}_{0}}}{S}y} + V_{{x}_{0}}}} & \left\lbrack {{Equation}3} \right\rbrack\end{matrix}$$V_{y} = {{\frac{2\left( {V_{{y}_{1}} - V_{{y}_{0}}} \right)}{S}x} + {\frac{V_{{y}_{2}} - V_{{y}_{0}}}{S}y} + V_{{y}_{0}}}$

Here, V_(x) and V_(y) represent an x component and a y component of amotion vector for a sample of the (x, y) coordinates in the currentblock, respectively, Vx₀ and Vy₀ represent an x component and a ycomponent of a motion vector V₀ for CP0 Vx₁ and Vy₁ represent an xcomponent and a y component of the motion vector V₁ for CP1, and Vx₂ andVy₂ represent an x component and a y component of the motion vector V₂for CP2, respectively. Equation 3 represents an equation for deriving asample unit motion vector considering that a width of the PU is S/2.According to the equation for deriving the sample unit motion vector asin Equation 3, a motion vector may be derived based on a relativeposition in the PU for each sample of the PU partitioned from the CUbased on the partitioning type N×2N.

FIG. 8 illustrates CPs of PUs partitioned from a CU based on thepartitioning type 2N×N. As illustrated in FIG. 8 , in order to derivethe sample unit motion vector, three CPs may be derived, and thepositions of the CPs may be adjusted as illustrated in FIG. 8 to adjusta height to S/2 according to the shape of the PU illustrated in FIG. 8 .That is, when a width and a height of the PU are S and S/2,respectively, and coordinates of the top-left sample position of the PUis (xp, yp), coordinates of CP0, among the CPs, may be (xp, yp),coordinates of CP1 is (xp+S, yp), and coordinates of CP2 may be (xp,yp+S/2). The sample unit motion vector may be derived based on thefollowing equation.

$\begin{matrix}{V_{x} = {{\frac{V_{{x}_{1}} - V_{{x}_{0}}}{S}x} + {\frac{2\left( {V_{{x}_{2}} - V_{{x}_{0}}} \right)}{S}y} + V_{{x}_{0}}}} & \left\lbrack {{Equation}4} \right\rbrack\end{matrix}$$V_{y} = {{\frac{V_{{y}_{1}} - V_{{y}_{0}}}{S}x} + {\frac{2\left( {V_{{y}_{2}} - V_{{y}_{0}}} \right)}{S}y} + V_{{y}_{0}}}$

Here, V_(x) and V_(y) represent an x component and a y component of amotion vector for a sample of the (x, y) coordinates in the currentblock, respectively, Vx₀ and Vy₀ represent an x component and a ycomponent of a motion vector V₀ for CP0, Vx₁ and Vy₁ represent an xcomponent and a y component of the motion vector V₁ for CP1, and Vx₂ andVy₂ represent an x component and a y component of the motion vector V₂for CP2, respectively. Equation 4 represents an equation for deriving asample unit motion vector considering that a height of the PU is S/2.According to the: equation for deriving the sample unit motion vector asin Equation 4, a motion vector may be derived based on a relativeposition in the PU for each sample of the PU partitioned from the CUbased on the partitioning type 2N×N.

FIG. 9 illustrates CPs of asymmetric PUs. The asymmetric PUs may be PUspartitioned from a CU based on the partitioning type nL×2N, nRx×2N,2N×nU, or 2N×nD.

As illustrated in FIG. 9 , widths and heights of the asymmetric PUs maybe W and H, respectively. In this case, an equation for deriving asample unit motion vector in the PU may be derived as follows. In orderto derive the sample unit motion vector, three CPs for each PU may bederived and coordinates of the CPs may be adjusted based on the widthand height according to the shape of the PU as illustrated in FIG. 9 .That is, when the width and height of the PU are W and H and coordinatesof a top-left sample position of each PU is (xp, yp), coordinates ofCP0, among the CPs, may be set to (xp, yp), coordinates of CP1 may beset to (xp+W, yp), and coordinates of CP2 may be set to (xp, yp+H). Inthis case, the sample unit motion vector in the PU may be derived basedon the following equation.

$\begin{matrix}{V_{x} = {{\frac{V_{{x}_{1}} - V_{{x}_{0}}}{W}x} + {\frac{V_{{x}_{2}} - V_{{x}_{0}}}{H}y} + V_{{x}_{0}}}} & \left\lbrack {{Equation}5} \right\rbrack\end{matrix}$$V_{y} = {{\frac{V_{{y}_{1}} - V_{{y}_{0}}}{W}x} + {\frac{V_{{y}_{2}} - V_{{y}_{0}}}{H}y} + V_{{y}_{0}}}$

Here, V_(x) and V_(y) represent an x component and a y component of amotion vector for a sample of the (x, y) coordinates in the currentblock, respectively, Vx₀ and Vy₀ represent an x component and a ycomponent of a motion vector V₀ for CP0, Vx₁ and Vy₁ represent an xcomponent and a y component of the motion vector V₁ for CP1, and Vx₂ andVy₂ represent an x component and a y component of the motion vector V₂for CP2, respectively. Equation 5 represents an equation for deriving asample unit motion vector considering the widths and the heights of theasymmetrical Pus. According to the equation for deriving the sample unitmotion vector as in Equation 5, a motion vector may be derived based ona relative position in the PU for each sample of the PU partitioned fromthe CU based on the partitioning type nL×2N, nRx×2N, 2N×nU, or 2N×nD.

Meanwhile, according to the present invention, in order to reduce motioninformation of CPs transmitted in units of PUs, e.g., three CPs, motioninformation prediction candidate for at least one CP may be selectedbased on motion information of a neighboring block or a neighboringsample of a PU. The motion information prediction candidate may becalled a motion information candidate or a motion vector candidate.

FIG. 10 illustrates motion information prediction candidates of CPs of aPU to which the partitioning type 2NX2N is applied. Referring to FIG. 10, a method of configuring motion information prediction candidates ofCPs is shown. Motion information of neighboring blocks (or neighboringsamples) adjacent to each CP may be used as prediction candidates formotion information of three CPs. In addition, motion information ofneighboring samples adjacent to each CP may be used as a motioninformation prediction candidate of each CP. For example, in the case ofmotion vector v0 of CP0, three pieces of motion information, amongpieces of motion information of previously decoded neighboring blocks(or neighboring samples), may be used as prediction candidates, and thethree pieces of motion information may be represented by A0, A1, and A2.In case where a width and a height of the PU are S and coordinates of atop-left sample position of the PU is (xp, yp), A0 is a motion vector ofa sample of (xp−1, yp−1) coordinates, and A1 may represent a motionvector of a sample of (xp, yp−1) coordinates, and A2 may represent amotion vector of a sample of (xp−1, yp) coordinates. In this case, atleast one of the motion vectors A0, A1 and A2 may be used as aprediction candidate of v0.

Also, in the case of the motion vector v1 of CP1, two pieces of motioninformation, among pieces of the motion information of the previouslydecoded neighboring blocks (or neighboring samples), may be used asprediction candidates, and the two pieces of motion information may berepresented by B0 and B1, respectively. In case where a width and aheight of the PU are S and coordinates of a top-left sample position ofthe PU is (xp, yp), B0 may represent a motion vector of a sample of(xp+S−1, yp−1) coordinates and B1 may represent a motion vector of asample of (xp+S−1, yp−1) coordinates. In this case, at least one of themotion vectors B0 and B1 may be used as a prediction candidate of v1.

Also, in the case of the motion vector v2 of CP2, two pieces of motioninformation, among pieces of the motion information of the previouslydecoded neighboring blocks (or neighboring samples), may be used asprediction candidates, and the two pieces of motion information may berepresented by C0 and C1, respectively. In case where a width and aheight of the PU are S and coordinates of a top-left sample position ofthe PU is (xp, yp), C0 may represent a motion vector of a sample of(xp−1, yp+S) coordinates and C1 may represent a motion vector of asample of (xp−1, yp+S−1) coordinates. In this case, at least one of themotion vectors C0 and C1 may be used as a prediction candidate of v2.

In this case, if an affine motion model is applied to a neighboringblock including a sample at a corresponding position, motion informationof the prediction candidate position may be derived based on a motionvector of the sample at the corresponding position, and if the affinemotion model is riot applied to the neighboring block including thesample at the corresponding position, motion information of theprediction candidate position may be derived based on a motion vector ofthe neighboring block including the sample at the correspondingposition. This is the same in the case of the other remainingembodiments of FIGS. 10 to 16 below. In detail, for example, in casewhere the affine motion model is applied to a neighboring blockincluding a sample of (xp−1, yp−1) coordinates, A0 may be derived basedon a motion vector of the sample of the (xp−1, yp−) coordinates, and incase where the affine motion model is not applied to a neighboring blockincluding a sample of (xp−1, yp−1) coordinates, A0 may be derived basedon a motion vector of a neighboring block including a sample of the(xp−1, yp−1) coordinates.

In this case, the numbers of prediction candidates for each CP in thefigure may serve to differentiate between prediction candidates or mayindicate a priority order of the prediction candidates. For example, inthe case of a prediction candidate for CP0, A0 may have a higherpriority over A1 and A1 may have a higher priority over A2. This is thesame for the case of the other remaining embodiments of FIGS. 11 to 16below

FIG. 11 illustrates motion information prediction candidates of CPs of aPU to which the partitioning type 2N×N is applied. Referring to FIG. 11, a method of configuring a motion information prediction candidate ofthe CPs is shown. As illustrated in FIG. 11 , a prediction candidate forthe motion vectors of the CPs may be configured in consideration of thefact that the PU does not have a square shape, and a predictioncandidate for the motion vectors of the CPs may be configured inconsideration of a decoding process order of the PU.

Motion information of neighboring blocks (or neighboring samples)adjacent to each CP may be used as prediction candidates for motioninformation of three CPs. When the affine motion model is applied to theneighboring blocks, motion information of neighboring samples adjacentto each CP may be used as a motion information prediction candidate ofeach CP. For example, in the case of motion vector v0 of CP0, threepieces of motion information, among pieces of motion information ofpreviously decoded neighboring blocks (or neighboring samples), may beused as prediction candidates, and the three pieces of motioninformation may be represented. by A0, A1, and A2. In case where a widthand a height of the PU are S and S/2, respectively, and coordinates of atop-left sample position of the PU is (xp, yp), A0 is a motion vector ofa sample of (xp−1, yp−1) coordinates, and A1 may represent a motionvector of a sample of (xp, yp−1) coordinates, and A2 may represent amotion vector of a sample of (xp−1, yp) coordinates. In this case, atleast one of the motion vectors A0, A1 and A2 may be used as aprediction candidate of v0.

Also, in the case of the motion vector v1 of CP1, two pieces of motioninformation, among pieces of the motion information of the previouslydecoded neighboring blocks (or neighboring samples), may be used asprediction candidates, and the two pieces of motion information may berepresented by B0 and B1, respectively. In case where a width and aheight of the PU are S and S/2, respectively, and coordinates of atop-left sample position of the PU is (xp, yp), B0 may represent amotion vector of a sample of (xp+S−1, yp−1) coordinates and B1 mayrepresent a motion vector of a sample of (xp+S−1, yp−1) coordinates. Inthis case, at least one of the motion vectors B0 and B1 may be used as aprediction candidate of v1.

Also, in the case of the motion vector v2 of CP2, two pieces of motioninformation, among pieces of the motion information of the previouslydecoded neighboring blocks (or neighboring samples), may be used asprediction candidates, and the two pieces of motion information may berepresented by C0 and C1, respectively. In case where a width and aheight of the PU are S and S/2, respectively, and coordinates of atop-left sample position of the PU is (xp, yp), C0 may represent amotion vector of a sample of (xp−1, yp+S/2) coordinates and C1 mayrepresent a motion vector of a sample of (xp−1, yp+S/2−1) coordinates.In this case, at least one of the motion vectors C0 and C1 may be usedas a prediction candidate of v2,

In another embodiment, when a partition ID of the PU is 1, samples ofneighboring blocks of the current CU may further be included asprediction candidates for the motion vector v0 of CP0 and the motionvector v1 of CP1. For example, in the case of the motion vector v0 ofCP0, motion information of a previously decoded neighboring block aneighboring block or a neighboring sample of the current CU) may furtherbe included as a prediction candidate. In detail, at least one of threepieces of motion information of neighboring samples may further be usedas a prediction candidate, and the three pieces of motion informationmay be represented by A3, A4, and A5, respectively. In case where awidth and a height of the CU including the PU are S and coordinates ofthe top-left sample position of the CU is (xc, yc), A3 may represent amotion vector of a sample of (xc−1, yc) coordinates, A4 may represent amotion vector of a sample of (xc−1, yc−1) coordinates, and A5 mayrepresent a motion vector of a sample of (xc, yc−1) coordinates. In thiscase, at least one of the motion vectors A3, A4, and A5 may further beused as a prediction candidate of v0.

Also, in the case of the motion vector v1 of CP1, motion information ofthe previously decoded neighboring blocks (or neighboring samples), maybe used as a prediction candidate. In detail, at least one of threepieces of motion information of neighboring samples may further be usedas a prediction candidate, and the three pieces of motion informationmay be represented by B2, B3, and B4, respectively. In case where awidth and a height of the CU including the PU are S and coordinates of atop-left sample position of the CU is (xc, yc), B2 may represent amotion vector of a sample of (xc+S, yc) coordinates, B3 may represent amotion vector of a sample of (xc+S−1, yc−1) coordinates, and B4 mayrepresent a motion vector of a sample of (xc+S−1, yc−1) coordinates. Inthis case, at least one of the motion vectors B2, B3, and B4 may furtherbe used as a prediction candidate of v1.

In another embodiment, each PU included in the CU may use the sameprediction candidates of the PUs in the CU, as prediction candidates forthe motion vectors of the CPs, regardless of partition ID. For example,in the case of the motion vector v0 of CP0 of each PU, three pieces ofmotion information, among pieces of the motion information of thepreviously decoded neighboring blocks (i.e., neighboring blocks orneighboring samples of the current CU), may be used as predictioncandidates, and the three pieces of motion information may berepresented by A0, A1, and A2, respectively. In case where a width and aheight of the CU are S and coordinates of the top-left sample positionof the CU is (xc, yc), A0 may represent a motion vector of a sample of(xc−1, yc−1) coordinates, A1 may represent a motion vector of a sampleof (xc, yc−1) coordinates, and A2 may represent a motion vector of asample of (xc−1, yc) coordinates. In this case, at least one of themotion vectors A0, A1 and A2 may be used as a prediction candidate ofv0.

Also, in the case of the motion vector v1 of CP1 of each PU, two piecesof motion information, among pieces of motion information of thepreviously decoded neighboring blocks (or neighboring samples) may beused as prediction candidates, and the two pieces of motion informationmay be represented by B0 and B1. In case where a width and a height ofthe CU are S and coordinates of the top-left sample position of the CUis (xc, yc), B0 may represent a motion vector of a sample of (xc+S,yc−1) coordinates and B1 may represent a motion vector of a sample of(xc+S−1, yc−1) coordinates. In this case, at least one of the motionvectors B0 and B1 may be used as a prediction candidate of v1.

Also, in the case of the motion vector v2 of CP2 of each PU, two piecesof motion information, among pieces of the motion information of thepreviously decoded neighboring blocks (or neighboring samples), may beused as prediction candidates, and the two pieces of motion informationmay be represented by C0 and C1, respectively. In case where a width anda height of the CU are S and coordinates of the top-left sample positionof the CU is (xc, yc), C0 may represent a motion vector of a sample of(xc−1, yc+S) coordinates and C1 may represent a motion vector of asample of (xc−1, yc+S−1) coordinates. In this case, at least one of themotion vectors C0 and C1 may be used as a prediction candidate of v2.

As a method of configuring; a prediction candidate for motion vectors ofCPs of a PU to which the 2N×N partitioning type is applied, predictioncandidates may be limited to a predetermined number so as to beconfigured.

FIG. 12 illustrates a configuration in which prediction candidates ofCPs of a PU to which the partitioning type 2N×N is applied are limitedto two prediction candidates. Referring to FIG. 12 , it is illustratedthat a list including two samples as prediction candidates of each CP ofthe PU is configured. For example, in the case of the motion vector v0of CP0, two pieces of motion information, among pieces of motioninformation of the previously decoded neighboring blocks (or neighboringsamples), may be used as prediction candidates, and the two pieces ofmotion information may be represented by A0 and A1. In case where awidth and a height of the PU are S and S/2, respectively, and thecoordinates of the top-left sample position of the PU is (xp, yp), A0may represent a motion vector of a sample of (xp−1, yp−1) coordinatesand A1 may represent a motion vector of a sample of (xp, yp−1)coordinates. In this case, A0 and A1 may be used as predictioncandidates of v0.

Also, in the case of the motion vector v1 of CP1, two pieces of motioninformation, among pieces of the motion information of the previouslydecoded neighboring blocks (or neighboring samples), may be used asprediction candidates, and the two pieces of motion information may berepresented by B0 and B1, respectively. In case where a width and aheight of the PU are S and S/2, respectively, and coordinates of atop-left sample position of the PU is (xp, yp), B0 may represent amotion vector of a sample of (xp+S−1, yp−1) coordinates and B1 mayrepresent a motion vector of a sample of (xp+S−1, yp−1) coordinates. Inthis case, the motion vectors B0 and B1 may be used as predictioncandidates of v1.

Also, in the case of the motion vector v2 of CP2, two pieces of motioninformation, among pieces of the notion information of the previouslydecoded neighboring blocks (or neighboring samples), may be used asprediction candidates, and the two pieces of motion information may berepresented by C0 and C1, respectively. In case where a width and aheight of the PU are S and S/2, respectively, and coordinates of atop-left sample position of the PU is (xp, yp), C0 may represent amotion vector of a sample of (xp−1, yp+S/2) coordinates and C1 mayrepresent a motion vector of a sample of (xp−1, yp+S/2−1) coordinates.In this case, the motion vectors C0 and C1 may be used as predictioncandidates of v2.

FIG. 13 illustrates motion information prediction candidates of CPs of aPU to which the partitioning type N×2N is applied. Referring to FIG. 13, a method of configuring motion information prediction candidates ofthe CPs is shown. As illustrated in FIG. 13 , a prediction candidate fora motion vector of the CPs may be configured in consideration of thefact that the PU does not have a square shape, and a predictioncandidate for a motion vector of the CPs may be configured inconsideration of a decoding processing order of the PU.

As illustrated in FIG. 13 , coded motion information of a neighboringblock (or neighboring sample) adjacent to each CP may be used asprediction candidates for motion information of three CPs. In case wherethe affine motion model is applied to the neighboring block, motioninformation of a neighboring sample adjacent to each CP may be used as amotion information prediction candidate of each CP. For example, in thecase of motion vector v0 of CP0, three pieces of motion information,among pieces of motion information of previously decoded neighboringblocks (or neighboring samples), may be used as prediction candidates,and the three pieces of motion information may be represented by A0, A1,and A2. In case where a width and a height of the PU are S/2 and S,respectively, and coordinates of a top-left sample position of the PU is(xp, yp), A0 is a motion vector of a sample of (xp−1, yp−1) coordinates,and A1 may represent a motion vector of a sample of (xp, yp−1)coordinates, and A2 may represent a motion vector of a sample of (xp−1,yp) coordinates. in this case, at least one of the motion vectors A0, A1and A2 may be used as a prediction candidate of v0.

Also, in the case of the motion vector v1 of CP1, two pieces of motioninformation, among pieces of the motion information of the previouslydecoded neighboring block (or neighboring sample), may be used asprediction candidates, and the two pieces of motion information may berepresented by B0 and B1, respectively. In case where a width and aheight of the PU are S/2 and S, respectively, and coordinates of atop-left sample position of the PU is (xp, yp), B0 may represent amotion vector of a sample of (xp+S/2, yp−1) coordinates and B1 mayrepresent a motion vector of a sample of (xp+S/2−1, yp−1) coordinates.In this case, at least one of the motion vectors B0 and B1 may be usedas a prediction candidate of v1. Also, in case where a partition ID ofthe PU is 0, at least one of a motion vector B2 of a sample of(xp+S/2+1, yp−1) coordinates and a motion vector B3 of a sample of(xp+S/2+2, yp−1) coordinates may further be included as a predictioncandidate of v1.

Also, in the case of the motion vector v2 of CP2, two pieces of motioninformation, among pieces of the motion information of the previouslydecoded neighboring block (or neighboring sample), may be used asprediction candidates, and the two pieces of motion information may berepresented by C0 andC 1, respectively. In case where a width and aheight of the PU are S/2 and S. respectively, and coordinates of atop-left sample position of the PU is (xp, yp), C0 may represent amotion vector of a sample of (xp−1, yp+S) coordinates and C1 mayrepresent a motion vector of a sample of (xp−1, yp+S−1) coordinates. Inthis case, at least one of the motion vectors C0 and C1 may be used as aprediction candidate of v2.

In another embodiment, when a partition ID of the PU is 1, samples ofneighboring blocks of the current CU may further be included asprediction candidates for the motion vector v0 of CP0 and the motionvector v2 of CP2. For example, in the case of the motion vector v0 ofCP0, motion information of a previously decoded neighboring block (i.e.,a neighboring block or a neighboring sample of the current CU) mayfurther be included as a prediction candidate. In detail, at least oneof three pieces of motion information of neighboring samples may furtherbe used as a prediction candidate, and the three pieces of motioninformation may be represented by A3, A4, and A5, respectively. In casewhere a width and a height of the CU including the PU are S andcoordinates of the top-left sample position of the CU is (xc, yc), A3may represent a motion vector of a sample of (xc−1, yc−1) coordinates,A4 may represent a motion vector of a sample of (xc, yc−1) coordinates,and A5 may represent a motion vector of a sample of (xc−1, yc)coordinates. In this case, at least one of the motion vectors A3, A4,and A5 may further be used as a prediction candidate of v0.

Also, in the case of the motion vector v2 of CP2, motion information ofthe previously decoded neighboring blocks (or neighboring samples), maybe used as a prediction candidate. In detail, at least one of threepieces of motion information of neighboring samples may further be usedas a prediction candidate, and the three pieces of motion informationmay be represented by C2, C3, and C4, respectively. In case where awidth and a height of the CU including the PU are S and coordinates of atop-left sample position of the CU is (xc, yc), C2 may represent amotion vector of a sample of (xc−1, yc+S) coordinates, C3 may representa motion vector of a sample of (xc, yc+S) coordinates, and C4 mayrepresent a motion vector of a sample of (xc−1, yc+S−1) coordinates. Inthis case, at least one of the motion vectors C2, C3, and C4 may furtherbe used as a prediction candidate of v2.

In another embodiment, each PU included in the CU may use the sameprediction candidates of the PUs in the CU, as prediction candidates forthe motion vectors of the CPs, regardless of partition ID. For example,in the case of the motion vector v0 of CP0 of each PU, three pieces ofmotion information, among pieces of the motion information of thepreviously decoded neighboring blocks (i.e., neighboring blocks orneighboring samples of the current CU), may be used as predictioncandidates, and the three pieces of motion information may berepresented by A0, A1, and A2, respectively. In case where a width and aheight of the CU are S and coordinates of the top-left sample positionof the CU is (xc, yc), A0 may represent a motion vector of a sample of(xc−1, yc−1) coordinates, A1 may represent a motion vector of a sampleof (xc, yc−1) coordinates, and A2 may represent a motion vector of asample of (xc−1, yc) coordinates. In this case, at least one of themotion vectors A0, A1 and A2 may be used as a prediction candidate ofv0.

Also, in the case of the motion vector v1 of CP1 of each PU, two piecesof motion information, among pieces of motion information of thepreviously decoded neighboring blocks (or neighboring samples) may beused as prediction candidates, and the two pieces of motion informationmay be represented by B0 and B1. In case where a width and a height ofthe CU are S and coordinates of the top-left sample position of the CUis (xc, yc), B0 may represent a motion vector of a sample of (xc+S,yc−1) coordinates and B1 may represent a motion vector of a sample of(xc+S−1, yc−1) coordinates. In this case, at least one of the motionvectors B0 and B1 may be used as a prediction candidate of v1.

Also, in the case of the motion vector v2 of CP2 of each PU, two piecesof motion information, among pieces of the motion information of thepreviously decoded neighboring blocks (or neighboring samples), may beused as prediction candidates, and the two pieces of motion informationmay be represented by C0 and C1, respectively. In case where a width anda height of the CU are S and coordinates of the top-left sample positionof the CU is (xc, yc), C0 may represent a motion vector of a sample of(xc−1, yc+S) coordinates and C1 may represent a motion vector of asample of (xc−1 , yc+S−1) coordinates. In this case, at least one of themotion vectors C0 and C1 may be used as a prediction candidate of v2.

As a method of configuring a prediction candidate for motion vectors ofCPs of a PU to which the N×2N partitioning type is applied, predictioncandidates may be limited to a predetermined number so as to beconfigured.

FIG. 14 illustrates a configuration in which prediction candidates ofCPs of a PU to which the partitioning type N×2N is applied a.re limitedto two prediction candidates. Referring to FIG. 14, it is illustratedthat a list including two samples as prediction candidates of each CP ofthe PU is configured. For example, in the case of the motion vector v0of CP0, two pieces of motion information, among pieces of motioninformation of the previously decoded neighboring blocks (or neighboringsamples), may be used as prediction candidates, and the two pieces ofmotion information may be represented by A0 and A1. In case where awidth and a height of the PU are S/2 and S, respectively, and thecoordinates of the top-left sample position of the PU is (xp, yp), A0may represent a motion vector of a sample of (xp−1, yp−1) coordinatesand A1 may represent a motion vector of a sample of (xp, yp−1)coordinates. in this case, A0 and A1 nay be used as predictioncandidates of v0.

Also, in the case of the motion vector v1 of CP1, two pieces of motioninformation, among pieces of the motion information of the previouslydecoded neighboring blocks (or neighboring samples), may be used asprediction candidates, and the two pieces of motion information may berepresented by B0 and B1, respectively. In case where a width and aheight of the PU are S/2 and S, respectively, and coordinates of atop-left sample position of the PU is (xp, yp), B0 may represent amotion vector of a sample of (xp+S/2, yp−1) coordinates and B1 mayrepresent a motion vector of a sample of (xp+S/2−1, yp−1) coordinates.In this case, the motion vectors B0 and B1 may be used as a predictioncandidate of v1.

Also, in the case of the motion vector v2 of CP2, two pieces of motioninformation, among pieces of the motion information of the previouslydecoded neighboring blocks (or neighboring samples), may be used asprediction candidates, and the two pieces of motion information may berepresented by C0 and C1, respectively. In case where a width nd aheight of the PU are S/2 and S, respectively, and coordinates of atop-left sample position of the PU is (xp, yp), C0 may represent amotion vector of a sample of (xp−1, yp+S) coordinates and C1 mayrepresent a motion vector of a sample of (xp−1, yp+S−1) coordinates. Inthis case, the motion vectors C0 and C1 may be used as a predictioncandidate of v2.

FIGS. 15A to 15D illustrate motion information prediction candidates ofCPs of asymmetric PUs. The asymmetric PUs may be PUs partitioned from aCU based on a partitioning type nL×2N, nR×2N, 2N×nU, or 2N×nD.

Referring to FIG. 15A, a method of configuring a motion informationprediction candidate of the CPs of a PU to which the partitioning typenL×2N is applied is shown. As illustrated in FIG. 15A, a predictioncandidate for a motion vector of the CPs may be configured inconsideration of the fact that the PU does not have a square shape, anda prediction candidate for a motion vector of the CPs may be configuredin consideration of decoding processing order of the PU.

As illustrated in FIG. 15A, coded motion information of neighboringblocks (or neighboring samples) adjacent to each CP may be used asprediction candidates for motion information of three CPs. When theaffine motion model is applied to the neighboring blocks, motioninformation of neighboring samples adjacent to each CP may be used as amotion information prediction candidate of each CP. For example, in thecase of motion vector v0 of CP0, three pieces of motion information,among pieces of motion information of previously decoded neighboringblocks (or neighboring samples), may be used as prediction candidates,and the three pieces of motion information may be represented by A0, A1,and A2. In case where a width and a height of the PU are W and H,respectively, and coordinates of a top-left sample position of the PU is(xp, yp), A0 is a motion vector of a sample of (xp−1, yp−1) coordinates,and A1 may represent a motion vector of a sample of (xp, yp−1)coordinates, and A2 may represent a motion vector of a sample of (xp−1,yp) coordinates. In this case, at least one of the motion vectors A0, A1and A2 may be used as a prediction candidate of v0.

Also, in the case of the motion vector v1 of CP1, two pieces of motioninformation, among pieces of the motion information of the previouslydecoded neighboring block (or neighboring sample), may be used asprediction candidates, and the two pieces of motion information may berepresented by B0 and B1, respectively. In case where a width and aheight of the PU are W and H, respectively, and coordinates of atop-left sample position of the PU is (xp, yp), B0 may represent amotion vector of a sample of (xp+W, yp−1) coordinates and B1 mayrepresent a motion vector of a sample of (xp+W−1, yp−1) coordinates. Inthis case, at least one of the motion vectors B0 and B1 may be used as aprediction candidate of v1.

Also, in the case of the motion vector v2 of CP2, two pieces of motioninformation, among pieces of the motion information of the previouslydecoded neighboring block (or neighboring sample), may be used asprediction candidates, and the two pieces of motion information may berepresented by C0 and C1, respectively. In case where a width and aheight of the PU are W and H, respectively, and coordinates of atop-left sample position of the PU is (xp, yp), C0 may represent amotion vector of a sample of (xp−1, yp+H) coordinates and C1 mayrepresent a motion vector of a sample of (xp−1, yp+H−1) coordinates. Inthis case, at least one of the motion vectors C0 and C1 may be used as aprediction candidate of v2.

In another embodiment, when a partition ID of the PU is 1, samples ofneighboring blocks of the current CU may further be included asprediction candidates for the motion vector v0 of CP0 and the motionvector v2 of CP2. For example, in the case of the motion vector v0 ofCP0. motion information of a previously decoded neighboring block (i.e.,a neighboring block or a neighboring sample of the current CU) mayfurther be included as a prediction candidate. In detail, at least oneof two pieces of motion information of neighboring samples may furtherbe used as a prediction candidate, and the two pieces of motioninformation may be represented by A3 and A4, respectively. In case wherea width and a height of the CU including the PU are H and coordinates ofthe top-left sample position of the CU is (xc, yc), A3 may represent amotion vector of a sample of (xc−1, yc−1) coordinates and A4 mayrepresent a motion vector of a sample of (xc−1, yc) coordinates. In thiscase, at least one of the motion vectors A3 and A4 may further be usedas a prediction candidate of v0.

Also, in the case of the motion vector v2 of the CP2, motion informationof a neighboring block (or a neighboring sample) previously decoded mayfurther be included as a prediction candidate. In detail, at least oneof two pieces of motion information of neighboring samples may furtherbe used as a prediction candidate, and the two pieces of motioninformation may be represented by C2 and C3, respectively. In case wherea width and a height of the CU including the PU are H and coordinates ofa top-left sample position of the CU is (xc, yc), C2 may represent amotion vector of a sample of (xc−1, yc+H) coordinates and C3 mayrepresent a motion vector of a sample of (xc−1, yc+H−1) coordinates. inthis case, at least one of the motion vectors C2 and C3 may further beused as a prediction candidate of v2.

Referring to FIG. 15B, a method of configuring a prediction candidatefor motion information of the CPs of a PU to which the partitioning typenR×2N is applied is shown. A prediction candidate for the motion vectorsof the CPs may be configured in consideration of the fact that the PUdoes not have a square shape, and a prediction candidate for the motionvectors of the CPs may be configured in consideration of decodingprocessing order of the PU.

As illustrated in FIG. 15B, coded motion information of a neighboringblock adjacent to each CP may be used as motion information predictioncandidates of three CPs. In case where the affine motion model isapplied to the neighboring block, motion information of a neighboringsample adjacent to each CP may be used as a prediction candidate formotion information of each CP. For example, in the case of motion vectorv0 of CP0, three pieces of motion information, among pieces of motioninformation of previously decoded neighboring blocks (or neighboringsamples), may be used as prediction candidates, and the three pieces ofmotion information may be represented by A0, A1, and A2. In case where awidth and a height of the PU are W and H, respectively, and coordinatesof a top-left sample position of the PU is (xp, yp), A0 is a motionvector of a sample of (xp−1, yp−1) coordinates, and A1 may represent amotion vector of a sample of (xp, yp−1) coordinates, and A2 mayrepresent a motion vector of a sample of (xp−1, yp) coordinates. In thiscase, at least one of the motion vectors A0, A1 and A2 may be used as aprediction candidate of v0.

Also, in the case of the motion vector v1 of CP1, two pieces of motioninformation, among pieces of the motion information of the previouslydecoded neighboring block (or neighboring sample), may be used asprediction candidates, and the two pieces of motion information may berepresented by B0 and B1 , respectively. In case where a width and aheight of the PU are W and H, respectively, and coordinates of atop-left sample position of the PU is (xp, yp), B0 may represent amotion vector of a sample of (xp+W, yp−1) coordinates and B1 mayrepresent a motion vector of a sample of (xp+W−1, yp−1) coordinates. Inthis case, at least one of the motion vectors B0 and B1 may be used as aprediction candidate of v1.

Also, in the case of the motion vector v2 of CP2, two pieces of motioninformation, among pieces of the motion information of the previouslydecoded neighboring block (or neighboring sample), may be used asprediction candidates, and the two pieces of motion information may berepresented by C0 and C1, respectively. In case where a width and aheight of the PU are W and H, respectively, and coordinates of atop-left sample position of the PU is (xp, yp), C0 may represent amotion vector of a sample of (xp−1, yp+H) coordinates and C1 mayrepresent a motion vector of a. sample of (xp−1, yp+H−1) coordinates. Inthis case, at least one of the motion vectors C0 and C1 may be used as aprediction candidate of v2.

In another embodiment, when a partition ID of the PU is 1, samples ofneighboring blocks of the current CU may further be included asprediction candidates for the motion vector v0 of CP0 and the motionvector v2 of CP2. For example, in the case of the motion vector v0 ofCP0, motion information of a previously decoded neighboring block (i.e.,a neighboring block or a neighboring sample of the current CU) mayfurther be included as a prediction candidate. In detail, at least oneof three pieces of motion information of neighboring samples may furtherbe used as a prediction candidate, and the three pieces of motioninformation may be represented by A3, A4, and AS, respectively. In casewhere a width and a height of the CU including the PU are H andcoordinates of the top-left sample position of the CU is (xc, yc), A3may represent a motion vector of a sample of (xc−1, yc−1) coordinates,A4 may represent a motion vector of a sample of (xc, yc−1) coordinates,and AS may represent a motion vector of a sample of (xc−1, yc)coordinates. In this case, at least one of the motion vectors A3, A4,and AS may further be used as a prediction candidate of v0.

Also, in the case of the motion vector v2 of CP2, motion information ofthe previously decoded neighboring block (or neighboring sample), may beused as a prediction candidate. In detail, at least one of three piecesof motion information of neighboring samples may further be used as aprediction candidate, and the three pieces of motion information may berepresented by C2, C3, and C4, respectively. In case where a width and aheight of the CU including the PU are H and coordinates of a top-leftsample position of the CU is (xc, yc), C2 may represent a motion vectorof a sample of (xc−1, yc+H) coordinates, C3 may represent a motionvector of a sample of (xc, yc+H) coordinates, and C4 may represent amotion vector of a sample of (xc−1, yc+H−1) coordinates. In this case,at least one of the motion vectors C2, C3, and C4 may further be used.as a prediction candidate of v2.

Referring to FIG. 15C, a method of configuring a prediction candidatefor motion information of the CPs of a PU to which the partitioning type2N×nU is applied is shown. As illustrated in FIG. 15C, a predictioncandidate for the motion vectors of the CPs may be configured inconsideration of the fact that the PU does not have a square shape, anda prediction candidate for the motion vectors of the CPs may beconfigured in consideration of decoding processing order of the PU.

As illustrated in FIG. 15C, coded motion information of a neighboringblock adjacent to each CP may be used as motion information predictioncandidates of the three CPs. In case where the affine motion model isapplied to the neighboring block, motion information of a neighboringsample adjacent to each CP may be used as a prediction candidate formotion information of each CP. For example, in the case of motion vectorv0 of CP0, three pieces of motion information, among pieces of motioninformation of previously decoded neighboring blocks (or neighboringsamples), may be used as prediction candidates, and the three pieces ofmotion information may be represented by A0, A1, and A2. In case where awidth and a height of the PU are W and H, respectively, and coordinatesof a top-left sample position of the PU is (xp, yp), A0 is a motionvector of a sample of (xp−1, yp−1) coordinates, and A1 may represent amotion vector of a sample of (xp, yp−1) coordinates, and A2 mayrepresent a motion vector of a sample of (xp−1, yp) coordinates. In thiscase, at least one of the motion vectors A0, A1 and A2 may be used as aprediction candidate of v0.

Also, in the case of the motion vector v1 of CP1, two pieces of motioninformation, among pieces of the motion information of the previouslydecoded neighboring block (or neighboring sample), may he used asprediction candidates, and the two pieces of motion information may berepresented by B0 and B1, respectively. In case where a width and aheight of the PU are W and H, respectively, and coordinates of atop-left sample position of the PU is (xp, yp), B0 may represent amotion vector of a sample of (xp+W, yp−1) coordinates and B1 mayrepresent a motion vector of a sample of (xp+W−1, yp−1) coordinates. Inthis case, at least one of the motion vectors B0 and B1 may be used as aprediction candidate of v1.

Also, in the case of the motion vector v2 of CP2, two pieces of motioninformation, among pieces of the motion information of the previouslydecoded neighboring block (or neighboring sample), may be used asprediction candidates, and the two pieces of motion information may berepresented by C0 and C1, respectively. In case where a width and aheight of the PU are W and H, respectively, and coordinates of atop-left sample position of the PU is (xp, yp), C0 may represent amotion vector of a sample of (xp−1, yp+H) coordinates and C1 mayrepresent a motion vector of a sample of (xp−1, yp30 H−1) coordinates.In this case, at least one of the motion vectors C0 and C1 may be usedas a prediction candidate of v2.

In another embodiment, when a partition ID of the PU is 1, samples ofneighboring blocks of the current CU may further be included asprediction candidates for the motion vector v0 of CP0 and the motionvector v1 of CP1 . For example, in the case of the motion vector v0 ofCP0, motion information of a previously decoded neighboring block (i.e.,a neighboring block or a neighboring sample of the current CU) mayfurther be included as a prediction candidate. In detail, at least oneof two pieces of motion information of neighboring samples may furtherbe used as a prediction candidate, and the two pieces of motioninformation may be represented by A3 and A4, respectively. In case wherea width and a height of the CU including the PU are W and coordinates ofthe top-left sample position of the CU is (xc, yc), A3 may represent amotion vector of a sample of (xc−1, yc−1) coordinates and A4 mayrepresent a motion vector of a sample of (xc, yc−1) coordinates. In thiscase, at least one of the motion vectors A3 and A4 may further be usedas a prediction candidate of v0.

Also, in the case of the motion vector v1 of the CP1, motion informationof a previously decoded neighboring block (or neighboring sample) mayfurther be included as a prediction candidate. In detail, at least oneof two pieces of motion information of neighboring samples may furtherbe used as a prediction candidate, and the two pieces of motioninformation may be represented by B2 and B3, respectively. In case wherea width and a height of a CU including the PU are W and coordinates of atop-left sample position of the CU is (xc, yc), B2 may represent amotion vector of a sample of (xc+S, yc−1) coordinates and B3 mayrepresent a motion vector of a sample of (xc+S−1, yc−1) coordinates. Inthis case, at least one of the motion vectors B2 and B3 may further beused as a prediction candidate of v1.

Referring to FIG. 15D, a method of configuring a prediction candidatefor motion information of the CPs of a PU to which the partitioning type2N×nD is applied is shown. As illustrated in FIG. 15D, a predictioncandidate for the motion vectors of the CPs may be configured inconsideration of the fact that the PU does not have a square shape, anda prediction candidate for the motion vectors of the CPs may beconfigured in consideration of decoding processing order of the PU.

As illustrated in FIG. 15D, coded motion information of a neighboringblock (or neighboring sample) adjacent to each CP may be used as aprediction candidate for motion information of the three CPs. In casewhere the affine motion model is applied to the neighboring block,motion information of a neighboring sample adjacent to each CP may beused as a motion information prediction candidate of each CP. Forexample, in the case of motion vector v0 of CP0, three pieces of motioninformation, among pieces of motion information of previously decodedneighboring blocks (or neighboring samples), may be used as predictioncandidates, and the three pieces of motion information may berepresented by A0, A1, and A2. In case where a width and a height of thePU are W and H, respectively, and coordinates of a top-left sampleposition of the PU is (xp, vp), A0 may be a motion vector of a sample of(xp−1, vp−1) coordinates. A1 may represent a motion vector of a sampleof (xp, yp−1) coordinates, and A2 may represent a motion vector of asample of (xp−1, yp) coordinates. In this case, at least one of themotion vectors A0, A1 and A2 may be used as a prediction candidate ofv0.

Also, in the case of the motion vector v1 of CP1, two pieces of motioninformation, among pieces of the motion information of the previouslydecoded neighboring block (or neighboring sample), may be used asprediction candidates, and the two pieces of motion information may berepresented by B0 and B1, respectively. In case where a width and aheight of the PU are W and H, respectively, and coordinates of atop-left sample position of the PU is (xp, yp), B0 may represent amotion vector of a sample of (xp+W, yp−1) coordinates and B1 mayrepresent a motion vector of a sample of (xp+W−1, yp−1) coordinates. Inthis case, at least one of the motion vectors B0 and B1 may be used as aprediction candidate of v1.

Also, in the case of the motion vector v2 of CP2, two pieces of motioninformation, among pieces of the motion information of the previouslydecoded neighboring block (or neighboring sample), may be used asprediction candidates, and the two pieces of motion information may berepresented by C0 and C1, respectively. In case where a width and aheight of the PU are W and H, respectively, and coordinates of atop-left sample position of the PU is (xp, yp), C0 may represent amotion vector of a sample of (xp−1, yp+H) coordinates and C1 mayrepresent a motion vector of a sample of (xp−1, yp+H−1) coordinates. Inthis case, at least one of the motion vectors C0 and C1 may be used as aprediction candidate of v2.

In another embodiment, when a partition ID of the PU is 1, samples ofneighboring blocks of the current CU may further be included asprediction candidates for the motion vector v0 of CP0 and the motionvector v1 of CP1. For example, in the case of the motion vector v0 ofCP0, motion information of a previously decoded neighboring block (i.e.,a neighboring block or a neighboring sample of the current CU) mayfurther be included as a prediction candidate. In detail, at least oneof three pieces of motion information of neighboring samples may furtherbe used as a prediction candidate, and the three pieces of motioninformation may be represented by A3, A4, and A5, respectively. In casewhere a width and a height of the CU including the PU are W andcoordinates of the top-left sample position of the CU is (xc, yc) A3 mayrepresent a motion vector of a sample of (xc−1, yc) coordinates, A4 mayrepresent a motion vector of a sample of (xc−1, yc−1) coordinates, andA5 may represent a motion vector of a sample of (xc, yc−1) coordinates.In this case, at least one of the motion vectors A3, A4, and A5 mayfurther be used as a prediction candidate of v0.

Also, in the case of the motion vector v1 of the CP1, motion informationof a previously decoded neighboring block (or neighboring sample) mayfurther be included as a prediction candidate. In detail, at least oneof three pieces of motion information of neighboring samples may furtherbe used as a prediction candidate, and the three pieces of motioninformation may be represented by B2, B3, and B4, respectively. In casewhere a width and a height of a CU including the PU are W andcoordinates of a top-left sample position of the CU is (xc, yc), B2 mayrepresent a motion vector of a sample of (xc+W, yc) coordinates, B3 mayrepresent a motion vector of a sample of (xc+W, yc−1) coordinates, andB4 may represent a motion vector of a sample of (xc+W−1, yc−1)coordinates. In this case, at least one of the motion vectors B2, B3,and B4 may further be used as a prediction candidate of v1.

Each PU included in the CU illustrated in FIGS. 15A to 15D may use thesame prediction candidates of the PUs in the CU as prediction candidatesfor the motion vectors of the CPs regardless of shape and partition ID.For example, in the case of the motion vector v0 of the CP0 of each PU,three pieces of motion information, among the pieces of motioninformation of the previously decoded neighboring blocks (i.e.,neighboring blocks or neighboring samples of the current CU), may beused as prediction candidates and the three pieces of motion informationmay be represented by A0, A1, and A2, respectively. In case where awidth and a height of the CU are W and H, respectively, and thecoordinates of the top-left sample position of the CU is (xc, yc), A0may represent a motion vector of a sample of (xc−1, yc−1) coordinates,A1 may represent a motion vector of a sample of (xc, yc−1) coordinates,and A2 may represent a motion vector of a sample of (xc−1, yc)coordinates. In this case, at least one of the motion vectors A0, A1 andA2 may be used as a prediction candidate of v0.

Also, in the case of the motion vector v1 of CP1 of each PU, two piecesof motion information, among pieces of motion information of thepreviously decoded neighboring blocks (or neighboring samples) may beused as prediction candidates, and the two pieces of motion informationmay be represented by B0 and B1. In case where a width and a height ofthe CU are W and coordinates of the top-left sample position of the CUis (xc, yc), B0 may represent a motion vector of a sample of (xc+W,yc−1) coordinates and B1 may represent a motion vector of a sample of(xc+W−1, yc−1) coordinates. In this case, at least one of the motionvectors B0 and B1 may be used as a prediction candidate of v1.

Also, in the case of the motion vector v2 of CP2 of each PU, two piecesof motion information, among pieces of the motion information of thepreviously decoded neighboring blocks (or neighboring samples), may beused as prediction candidates, and the two pieces of motion informationmay be represented by C0 and C1, respectively. In case where a width anda height of the CU are W and coordinates of the top-left sample positionof the CU is (xc, yc), C0 may represent a motion vector of a sample of(xc−1, yc+H) coordinates and C1 may represent a motion vector of asample of (xc−1, yc+H−1) coordinates. In this case, at least one of themotion vectors C0 and C1 may be used as a prediction candidate of v2.

As a method of configuring a prediction candidate for motion vectors ofCPs of a PU to which the nL×2N, nR×2N, 2N×nU, or 2N×nD partitioning typeis applied, prediction candidates may be limited to a predeterminednumber so as to be configured.

FIG. 16 illustrates a configuration in which prediction candidates ofCPs of asymmetric PUs are limited to two prediction candidates. Theasymmetric PUs may be PUs partitioned from a CU based on thepartitioning type nL×2N, nR×2N, 2N×nU, or 2N×nD.

Referring to FIG. 16 , a configuration in which prediction candidates ofeach CP of each PU is limited to two prediction candidates isillustrated. For example, in the case of the motion vector v0 of CP0,two pieces of motion information, among pieces of motion information ofthe previously decoded neighboring blocks (or neighboring samples), maybe used as prediction candidates, and the two pieces of motioninformation may be represented by A0 and A1. In case where a width and aheight of the PU are W and H, respectively, and the coordinates of thetop-left sample position of the PU is (xp, yp), A0 may represent amotion vector of a sample of (xp−1, yp−1) coordinates and A1 mayrepresent a motion vector of a sample of (xp, yp−1) coordinates. In thiscase, A0 and A1 may be used as prediction candidates of v0.

Also, in the case of the motion vector v1 of CP1, two pieces of motioninformation, among pieces of the motion information of the previouslydecoded neighboring blocks (or neighboring samples), may be used asprediction candidates, and the two pieces of motion information may berepresented by B0 and B1, respectively. In case where a width and aheight of the PU are W and respectively, and coordinates of a top-leftsample position of the PU is (xp, yp), B0 may represent a motion vectorof a sample of (xp+W yp−1) coordinates and B1 may represent a motionvector of a sample of (xp+W−1, yp−1) coordinates. In this case, themotion vectors B0 and B1 may be used as a prediction candidate of v1.

Also, in the case of the motion vector v2 of CP2, two pieces of motioninformation, among pieces of the motion information of the previouslydecoded neighboring blocks (or neighboring samples), may be used asprediction candidates, and the two pieces of motion information may berepresented by C0 and C1, respectively. In case where a width and aheight of the PU are W and H, respectively, and coordinates of atop-left sample position of the PU is (xp, yp), C0 may represent amotion vector of a sample of (xp−1, yp+H) coordinates and C1 mayrepresent a motion vector of a sample of (xp−1, yp+H−1) coordinates. Inthis case, the motion vectors C0 and C1 may be used as a predictioncandidate of v2.

Meanwhile, when the motion vector of each CP is derived as described inthe aforementioned embodiment, an amount of data for motion informationmay slightly be increased. A method of reducing the amount of data usingthe characteristics that each CP is located at the boundary of thecurrent PU may be used.

If a CP of a PU (next PU) to be decoded next to the current PU has thesame position as the CP of the current PU, the encoding device may notseparately code motion information on the CP of the next PU, and may usea method of coding using the above-described prediction candidates onlyfor the CP in the case where motion information is not present in aprevious decoding process.

FIG. 17 illustrates a PU including a CP for which motion informationcoding is required and a CP for which motion information coding is notrequired. Whether or not a PU is a PU for which motion information isrequired may be determined by checking a decoding process of motioninformation of a neighboring block of a current PU within the encodingdevice/decoding device. Therefore, transmission of additional syntaxinformation may not be required in determining whether the PU is a PUfor which motion information is required. Referring to FIG. 17 , CPs ofthe current PU is illustrated, The top-left, sample of the current PUmay be referred to as CP0, the upper right neighboring sample of thecurrent PU may be referred to as CP1, and the bottom-left neighboringsample of the current PU may be referred to as CP2. In case where theblocks are coded according to raster scan order, it may be determinedthat the right block of the current PU has not been decoded yet. Thus,it may be determined that motion information for the CP located at theright block needs to be coded. For example, since motion vectors of theCPs, excluding CPI, have been derived in a process of decoding previousPUs, the encoding device may code only motion information for the CP1and transmit the coded motion information through a bit stream.

FIG. 18 illustrates a PU including CPs for which motion informationcoding is not required. Referring to FIG. 18 , motion information of asample in which CPs of a current PU are located has already been derivedfrom an upper block of the current PU. Accordingly, the encoding devicemay code the corresponding motion information without decodingadditional motion information That is, the decoding device may derive amotion vector of the CPs of the current PU based on a motion vectorderived in the previous decoding process, without receiving additionalmotion information.

For example, in the case of CP0, in case where an uppermost block, amongleft neighboring blocks adjacent to a left boundary of the currentblock, is decoded based on the affine motion model, a motion vector ofCP1 of the corresponding block may be used as a motion vector of CP0 ofthe current block. Also, in case where a leftmost block, among upperneighboring blocks adjacent to an upper boundary of the current block,is decoded based on the affine motion model, a motion vector of CP2 ofthe corresponding block may be used as a motion vector of CP0 of thecurrent block. Also, in case where an upper left neighboring block ofthe current block is decoded based on the affine motion model, a motionvector of a lower right neighboring sample of the corresponding blockderived based on the CPs of the corresponding block may be used as amotion vector of CP0 of the current block. In this case, the motionvector of the lower right neighboring sample of the corresponding blockmay be derived based on the CPs of the corresponding block based onEquations 2 to 5 described above.

For example, in the case of CPI, in case where an upper rightneighboring block of the current block is decoded based on the affinemotion model, a motion vector of CP2 of the corresponding block may beused as a motion vector of CP1 of the current block. In case where arightmost block of the upper neighboring blocks adjacent to the upperboundary of the current block is decoded based on the affine motionmodel, a motion vector of a lower right neighboring sample of thecorresponding block derived based on the CPs of the block may be used asa motion vector of CP1 of the current block. In this case, the motionvector of the lower right neighboring samples of the corresponding blockmay be derived based on the CPs of the corresponding block based onEquations 2 to 5 described above.

For example, in the case of CP2, in case where a lower left neighboringblock of the current block is decoded based on the affine motion model,a motion vector of CP1 of the corresponding block may be used as amotion vector of CP2 of the current block. Also, in case where alowermost block of left neighboring blocks adjacent to a left boundaryof the current block is decoded based on the affine motion model, amotion vector of a lower tight neighboring sample of the correspondingblock derived based on the CPs of the current block may be used as amotion vector of CP2 of the current block. In this case, the motionvector of the lower right neighboring sample of the corresponding blockmay be derived based on the CPs of the corresponding block based onEquations 2 to 5 described above.

FIG. 19 schematically illustrates a video encoding method by an encodingdevice according to the present invention. The method disclosed in FIG.19 may be performed by the encoding device disclosed in FIG. 1 .Specifically, for example, steps S1900 to S1930 of FIG. 19 may beperformed by the predicting unit of the encoding device, and step S1940may be performed by the entropy-encoding unit of the encoding device.

The encoding device derives control points (CPs) for a current block(S1900). The encoding device may determine whether to apply the affinemotion model of the current block based on an RD cost. In case where theaffine motion model is applied to the current block, the encoding devicemay derive CPs to apply the affine motion model. The CPs may be threeCPs.

For example, in case where the current block is a PU partitioned from aCU based on the partitioning type 2N×2N and a width and a height of thecurrent block are S, the encoding device may derive three CPs in whichCP0 is a sample of (0, 0) coordinates, CP1 is a sample of (S, 0)coordinates, and CP2 is a sample of (0, S) coordinates based oncoordinates (0, 0) of the top-left sample position of the current block.

Also, in case where the current block is a PU partitioned from a CUbased on the partitioning type N×2N and a width and a height of thecurrent block are S/2 and S, respectively, the encoding device mayderive three CPs in which CP0 is a sample of (0, 0) coordinates, CP1 isa sample of (S/2, 0) coordinates, and CP2 is a sample of (0, S)coordinates based on the coordinates (0, 0) of the top-left sampleposition of the current block.

Also, in case where the current block is a PU partitioned from a CUbased on the partitioning type 2N×N and a width and a height of thecurrent block are S and S/2, respectively, the encoding device mayderive three CPs in which CP0 is a sample of (0, 0) coordinates, CP1 isa sample of (S/2, 0) coordinates, and CP2 is a sample of (0, S/2)coordinates based on the coordinates (0, 0) of the top-left sampleposition of the current block.

Also, in case where the current block is a PU partitioned from a CUbased on the partitioning type nL×2N, nR×2N, 2N×nU, or 2N×nD and a widthand a height of the current block are W and H, respectively, theencoding device may derive three CPs in which CP0 is a sample of (0, 0)coordinates, CP1 is a sample of (W, 0) coordinates, and CP2 is a sampleof (0, H) coordinates based on the coordinates (0, 0) of the top-leftsample position of the current block.

The encoding device obtains motion vectors for the CPs (S1910). Theencoding device may derive motion vectors for the CPs based onneighboring samples adjacent to the CPs. The samples adjacent to the CPsmay be configured as prediction candidates. The encoding device mayconfigure prediction candidates for the motion vectors of the CPs basedon coded motion information of neighboring blocks (or samples) adjacentto each CP and derive a motion vector of each CP based on anoptimalandidate among the configured prediction candidates. Theprediction candidates may be determined based on a partitioning type, apartition ID, and a shape of the current block.

For example, in case where the current block is a PU to which thepartitioning type 2N×2N is applied, in the case of the motion vector v0of CP0, the encoding device may use three pieces of motion information,among pieces of motion information of neighboring blocks (or neighboringsamples), as prediction candidates, and the three pieces of motioninformation may be represented by A0, A1, and A2, respectively. In casewhere a width and a height of the current block are S and coordinates ofa top-left sample position of the current block is (xp, yp), A0 mayrepresent a motion vector of a sample of (xp−1, yp−1) coordinates, A1may represent a motion vector of a sample of (xp, yp−1) coordinates, andA2 may represent a motion vector of a sample of (xp−1, yp) coordinates.In this case, the encoding device may use at least one of the motionvectors A0, A1 and A2 as a prediction candidate of v0. That is, theencoding device may derive the motion vector v0 regarding CP0 based on aneighboring sample group 0 including the sample of the (xp−1, yp−1)coordinates, the sample of the (xp, yp−1) coordinates, and the sample ofthe (xp−1, yp) coordinates.

Also, in the case of the motion vector v1 of CP1, the encoding devicemay use two pieces of motion information, among pieces of motioninformation of neighboring blocks (or neighboring samples), asprediction candidates, and the two pieces of motion information may berepresented by B0 and B1. In case where a width and a height of thecurrent block are S and coordinates of a top-left sample position of thecurrent block is (xp, yp), B0 may represent a motion vector of a sampleof (xp+S, yp−1) coordinates and B1 may represent a motion vector of asample of (xp+S−1, yp−1) coordinates. In this case, the encoding devicemay use at least one of the motion vectors B0 and B1 as a predictioncandidate of v1. That is, the encoding device may derive the motionvector v1 regarding CP1 based on a neighboring sample group 1 includingthe sample of the (xp+S, yp−1) coordinates and the sample of the(xp+S−1, yp−1) coordinates.

Also, in the case of the motion vector v2 of CP2, the encoding devicemay use two pieces of motion information, among pieces of motioninformation of neighboring blocks (or neighboring samples), asprediction candidates, and the two pieces of motion information may berepresented by C0 and C1. In case where a width and a height of thecurrent block are S and coordinates of a top-left sample position of thecurrent block is (xp, yp), C0 may represent a motion vector of a. sampleof (xp−1, yp+S) coordinates and C1 may represent a motion vector of asample of (xp−1, yp+S−1) coordinates. In this case, the encoding devicemay use at least one of the motion vectors C0 and C1 as a predictioncandidate of v2. That is, the encoding device may derive the motionvector v2 regarding CP2 based on a neighboring sample group 2 includingat least one of the sample of the (xp−1, yp+S) coordinates and thesample of the (xp−1, yp+S−1) coordinates.

In another example, in case where the current block is a PU to which thepartitioning type 2N×N is applied, in the case of the motion vector v0of CP0, the encoding device may use three pieces of motion information,among pieces of motion information of neighboring blocks (or neighboringsamples), as prediction candidates, and the three pieces of motioninformation may be represented by A0, A1, and A2, respectively. In casewhere a width and a height of the current block are S and S/2,respectively, and coordinates of a top-left sample position of thecurrent block is (xp, yp), A0 may represent a motion vector of a sampleof (xp−1, yp−1) coordinates, A1 may represent a motion vector of asample of (xp, yp−1) coordinates, and A2 may represent a motion vectorof a sample of (xp−1, yp) coordinates. In this case, the encoding devicemay use at least one of the motion vectors A0, A1 and A2 as a predictioncandidate of v0. That is, the encoding device may derive the motionvector v0 regarding CP0 based on a neighboring sample group 0 includingat least one of the sample of the (xp−1, yp−1) coordinates, the sampleof the (xp, yp−1) coordinates, and the sample of the (xp−1, yp)coordinates.

Also, in the case of the motion vector v1 of CP1, the encoding devicemay use two pieces of motion information, among pieces of motioninformation of neighboring blocks (or neighboring samples), asprediction candidates, and the two pieces of motion information may berepresented by B0 and B1. In case where a width and a height of thecurrent block are S and S/2, respectively, and coordinates of a top-leftsample position of the current block is (xp, yp), B0 may represent amotion vector of a sample of (xp+S, yp−1) coordinates and B1 mayrepresent a motion vector of a sample of (xp+S−1, yp−1) coordinates. Inthis case, the encoding device may use at least one of the motionvectors B0 and B 1as a prediction candidate of v1. That is, the encodingdevice may derive the motion vector v1 regarding CP1 based on aneighboring sample group 1 including at least one of the sample of theyp−1) coordinates and the sample of the (xp+S−1, yp−1) coordinates.

Also, in the case of the motion vector v2 of CP2, the encoding devicemay use two pieces of motion information, among pieces of motioninformation of neighboring blocks (or neighboring samples), asprediction candidates, and the two pieces of motion information may berepresented by C0 and C1. In case where a width and a height of thecurrent block are S and S/2, respectively, and coordinates of a top-leftsample position of the current block is (xp, yp), C0 may represent amotion vector of a sample of (xp−1, yp+S/2) coordinates and C1 mayrepresent a motion vector of a sample of (xp−1, yp+S/2−1) coordinates.In this case, the encoding device may use at least one of the motionvectors C0 and C1 as a prediction candidate of v2. That is, the encodingdevice may derive the motion vector v2 regarding CP2 based on aneighboring sample group 2 including at least one of the sample of the(xp−1, yp+S/2) coordinates and the sample of the (xp−1, yp+S/2−1)coordinates.

In case where a partition ID of the current block is 1, the encodingdevice may further include samples of neighboring blocks of the currentCU as prediction candidates for the motion vector v0 of CP0 and themotion vector v1 of CP1. For example, in the case of the motion vectorv0 of CP0, the encoding device may further include motion information ofneighboring blocks (i.e., neighboring samples) as a predictioncandidate. In detail, the encoding device may further use at least oneof three pieces of motion information of neighboring samples as aprediction candidate, and the three pieces of motion information may berepresented by A3, A4, and A5, respectively. In case where a width and aheight of the CU including the current block are S and coordinates ofthe top-left sample position of the CU is (xc, yc), A3 may represent amotion vector of a sample of (xc−1, yc) coordinates, A4 may represent amotion vector of a sample of (xc−1, yc−1) coordinates, and A5 mayrepresent a motion vector of a sample of (xc, yc−1) coordinates. In thiscase, the encoding device may further use at least one of the motionvectors A3, A4, and A5 as a prediction candidate of v0. That is, theencoding device may further include at least one of the sample of the(xc−1, yc−1) coordinates, the sample of the (xc−1, yc) coordinates, andthe sample of the (xc, yc−1) coordinates in the neighboring sample group0.

Also, in the case of the motion vector v1 of CP1, the encoding devicemay further include motion information of a neighboring block of thecurrent CU as a prediction candidate. In detail, the encoding device mayfurther use at least one of three pieces of motion information ofneighboring samples as a prediction candidate, and the three pieces ofmotion information may be represented by B2, B3, and B4, respectively.In case where a width and a height of the CU including the current blockare S and coordinates of the top-left sample position of the CU is (xc,yc), B2 may represent a motion vector of a sample of (xc+S, yc)coordinates, B3 may represent a

motion vector of a sample of (xe+S, yc−1) coordinates, and B4 mayrepresent a motion vector of a sample of (xc+S−1, yc−1) coordinates. Inthis case, the encoding device may further use at least one of themotion vectors B2, B3, and B4 as a prediction candidate of v1. That is,the encoding device may further include at least one of the sample ofthe (xc+S, yc) coordinates, the sample of the (xc+S, yc−1) coordinates,and the sample of the (xc+S−1, yc−1) coordinates in the neighboringsample group 1.

Also, the encoding device may configure the prediction candidates forthe motion vectors of the CPs of the current block by limiting thenumber of prediction candidates to a certain number. In the case of themotion vector v0 of CP0, the encoding device may use two pieces ofmotion information, among pieces of motion information of theneighboring blocks (or neighboring samples), as prediction candidates,and the two pieces of motion information may be represented by A0 andA1. In case where a width and a height of the current block are S andS/2, respectively, and the coordinates of the top-left sample positionof the current block is (xp, yp), A0 may represent a motion vector of asample of (xp−1, yp−1) coordinates and A1 may represent a motion vectorof a sample of (xp, yp−1) coordinates. In this case, the encoding devicemay use A0 and Al as prediction candidates of v0. That is, the encodingdevice may include the sample of the (xp−1, yp−1) coordinates and thesample of the (xp, yp−1) coordinates in the neighboring sample group 0,and availability of the sample of the (xp−1, yp−1) coordinates and thesample of the (xp, yp−1) coordinates may be sequentially determinedaccording to first predefined priority order.

In the case of the motion vector v1 of CP1, the encoding device may usetwo pieces of motion information, among pieces of motion information ofthe neighboring blocks neighboring samples), as prediction candidates,and the two pieces of motion information may be represented by B0 andB1. In case where a width and a height of the current block are S andS/2, respectively, and the coordinates of the top-left sample positionof the current block is (xp, yp), B0 may represent a motion vector of asample of (xp+S, yp−1) coordinates and B1 may represent a motion vectorof a sample of (xp+S-1, yp−1) coordinates. In this case, the encodingdevice may use B0 and B1 as prediction candidates of v1. That is, theencoding device may include the sample of the (xp+S, yp−1) coordinatesand the sample of the (xp+S−1, yp−1) coordinates in the neighboringsample group 1, and availability of the sample of the (xp+S, yp−1)coordinates and the sample of the (xp+S−1, yp−1) coordinates may besequentially determined according to second predefined priority order.

In the case of the motion vector v2 of CP2, the encoding device may usetwo pieces of motion information, among pieces of motion information ofthe neighboring blocks (or neighboring samples), as predictioncandidates, and the two pieces of motion information may be representedby C0 and C1. In case where a width and a height of the current blockare S and S/2, respectively, and the coordinates of the top-left sampleposition of the current block is (xp, yp), C0 may represent a motionvector of a sample of (xp−1, yp+S/2) coordinates and C1 may represent amotion vector of a. sample of (xp−1, yp+S/2−1) coordinates. In thiscase, the encoding device may use C0 and C1 as prediction candidates ofv2. That is, the encoding device may include the sample of the (xp−1,yp+S/2) coordinates and the sample of the (xp−1, yp+S/2−1) coordinatesin the neighboring sample group 2, and availability of the sample of the(xp−1, yp+S/2) coordinates and the sample of the (xp−1, yp+S/2−1)coordinates may be sequentially determined according to third predefinedpriority order.

In another example, in case where the current block is a PU to which thepartitioning type N×2N is applied, in the case of the motion vector v0of CP0, the encoding device may use three pieces of motion information,among pieces of motion information of neighboring blocks (or neighboringsamples), as prediction candidates, and the three pieces of motioninformation may be represented by A0, A1, and A2, respectively. In casewhere a width and a height of the current block are S/2 and S,respectively, and coordinates of a top-left sample position of thecurrent block is (xp, yp), A0 may represent a motion vector of a sampleof (xp−1, yp−1) coordinates, A1 may represent a motion vector of asample of (xp, yp−1) coordinates, and A2 may represent a motion vectorof a sample of (xp−1, yp) coordinates, In this case, the encoding devicemay use at least one of the motion vectors A0, A1 and A2 as a predictioncandidate of v0. That is, the encoding device may derive the motionvector v0 regarding CP0 based on a neighboring sample group 0 includingthe sample of the (xp−1, yp−1) coordinates, the sample of the (xp, yp−1)coordinates, and the sample of the (xp−1, yp) coordinates.

Also, in the case of the motion vector v1 of CP1, the encoding devicemay use two pieces of motion information, among pieces of motioninformation of neighboring blocks (or neighboring samples), asprediction candidates, and the two pieces of motion information may berepresented by B0 and B1. In case where a width and a height of thecurrent block are S/2 and S, respectively, and coordinates of a top-leftsample position of the current block is (xp, yp), B0 may represent amotion vector of a sample of (xp+S/2, yp−1) coordinates and B1 mayrepresent a motion vector of a sample of (xp+S/2−1, yp−1) coordinates.In this case, the encoding device may use at least one of the motionvectors B0 and B1 as a prediction candidate of vi. Also, in case where apartition ID of the current block is 0, the encoding device may furtherinclude at least one of the motion vector B2 of the sample of the(xp+S/2+1, yp−1) coordinates and the motion vector B3 of the sample ofthe (xp+S/2+2, yp−1) coordinates as a prediction candidate of v1. Thatis, the encoding device may derive the motion vector v1 regarding CP1based on the neighboring sample group 1 including the sample of the(xp+S/2, yp−1) coordinates and the sample of the (xp+S/2−1, yp−1)coordinates.

Also, in the case of the motion vector v2 of CP2, the encoding devicemay use two pieces of motion information, among pieces of motioninformation of neighboring blocks (or neighboring samples), asprediction candidates, and the two pieces of motion information may berepresented by C0 and C1. In case where a width and a height of thecurrent block are S/2 and S, respectively, and coordinates of a top-leftsample position of the current block is (xp, yp), C0 may represent amotion vector of a sample of (xp−1, yp+S) coordinates and C1 mayrepresent a motion vector of a sample of yp+S−1) coordinates. In thiscase, the encoding device may use at least one of the motion vectors C0and C1 as a prediction candidate of v2. That is, the encoding device mayderive the motion vector v2 regarding CP2 based on the neighboringsample group 2 including the sample of the (xp−1, yp+S) coordinates andthe sample of the (xp−1, yp+S−1) coordinates.

In case where a partition ID of the current block is 1, the encodingdevice may further include samples of neighboring blocks of the currentCU as prediction candidates for the motion vector v0 of CP0 and themotion vector v2 of CP2. For example, in the case of the motion vectorv0 of CP0, the encoding device may further include motion information ofneighboring blocks (i.e., neighboring samples) as a predictioncandidate. In detail, the encoding device may further use at least oneof three pieces of motion information of neighboring samples as aprediction candidate, and the three pieces of motion information may berepresented by A3, A4, and A5, respectively. In case where a width and aheight of the CU including the current block are S and coordinates ofthe top-left sample position of the CU is (xc, yc), A3 may represent amotion vector of a sample of (xc−1, yc−1) coordinates, A4 may representa motion vector of a sample of (xc, yc−1) coordinates, and A5 mayrepresent a motion vector of a sample of (xc−1, yc) coordinates. In thiscase, the encoding device may further use at least one of the motionvectors A3, A4, and A5 as a prediction candidate of v0. That is, theencoding device may further include at least one of the sample of the(xc−1, yc−1) coordinates, the sample of the (xc−1, yc) coordinates, andthe sample of the (xc, yc−1) coordinates in the neighboring sample group0.

Also, in the case of the motion vector v2 of CP2, the encoding devicemay further include motion information of neighboring blocks (orneighboring samples) as a prediction candidate. In detail, the encodingdevice may further use at least one of three pieces of motioninformation of neighboring samples as a prediction candidate, and thethree pieces of motion information may be represented by C2, C3, and C4,respectively. In case where a width and a height of the CU including thecurrent block are S and coordinates of the top-left sample position ofthe CU is (xc, ye), C2 may represent a motion vector of a sample of(xc−1, yc+S) coordinates, C3 may represent a motion vector of a sampleof (xc, yc+S) coordinates, and C4 may represent a motion vector of asample of (xc−1, yc+S−1) coordinates. In this case, the encoding devicemay further use at least one of the motion vectors C2, C3, and C4 as aprediction candidate of v2. That is, the encoding device may furtherinclude at least one of the sample of the (xc−1, yc+S−1) coordinates,the sample of the (xc, yc+S) coordinates, and the sample of the (xc−1,yc+S−1) coordinates in the neighboring sample group 2.

Also, the encoding device may configure the prediction candidates forthe motion vectors of the CPs of the current block by limiting thenumber of prediction candidates to a certain number. In the case of themotion vector v0 of CPU, the encoding device may use two pieces ofmotion information, among pieces of motion information of theneighboring blocks (or neighboring samples), as prediction candidates,and the two pieces of motion information may be represented by A0 andA1. In case where a width and a height of the current block are S/2 andS, respectively, and the coordinates of the top-left sample position ofthe current block is (xp, yp), A0 may represent a motion vector of asample of (xp−1, yp−1) coordinates and A1 may represent a motion vectorof a sample of (xp, yp−1) coordinates. In this case, the encoding devicemay use A0 and A1 as prediction candidates of v0. That is, the encodingdevice may include the sample of the (xp−1, yp−1) coordinates and thesample of the (xp, yp−1) coordinates in the neighboring sample group 0,and availability of the sample of the (xp−1, yp−1) coordinates and thesample of the (xp, yp−1) coordinates may be sequentially determinedaccording to first predefined priority order.

In the case of the motion vector v1 of CP1, the encoding device may usetwo pieces of motion information, among pieces of motion information ofthe neighboring blocks (or neighboring samples), as predictioncandidates, and the two pieces of motion information may be representedby B0 and B1. in case where a width and a height of the current blockare S/2 and S, respectively, and the coordinates of the top-left sampleposition of the current block is (xp, yp), B0 may represent a motionvector of a sample of (xp+S/2, yp−1) coordinates and B1 may represent amotion vector of a sample of (xp+S/2−1, yp−1) coordinates. In this case,the encoding device may use B0 and B1 as prediction candidates of v1.That is, the encoding device may include the sample of the (xp+S/2,yp−1) coordinates and the sample of the (xp+S/2−1, yp−1) coordinates inthe neighboring sample group 1, and availability of the sample of the(xp+S/2, yp−1) coordinates and the sample of the (xp+S/2−1, yp−1)coordinates may he sequentially determined according to secondpredefined priority order.

Also, in the case of the motion vector v2 of CP2, the encoding devicemay use two pieces of motion information, among pieces of motioninformation of the neighboring blocks (or neighboring samples), asprediction candidates, and the two pieces of motion information may berepresented by C0 and C1. In case where a width and a height of thecurrent block are S/2 and S, respectively, and the coordinates of thetop-left sample position of the current block is (xp, yp), C0 mayrepresent a motion vector of a sample of (xp−1, yp+S) coordinates and C1may represent a motion vector of a sample of (xp−1, yp+S−1) coordinates.In this case, the encoding device may use C0 and C1 as predictioncandidates of v2, That is, the encoding device may include the sample ofthe (xp−1, yp+S) coordinates and the sample of the (xp−1, yp+S−1)coordinates in the neighboring sample group 2, and availability of thesample of the (xp−1, yp+S/2) coordinates and. the sample of the (xp−1,yp+S/2−1) coordinates may be sequentially determined according to thirdpredefined priority order.

In another example, in case where the current block is a PU to which thepartitioning type nL×2N is applied, for example, in the case of themotion vector v0 of CP0, the encoding device may use three pieces ofmotion information, among pieces of motion information of neighboringblocks (or neighboring samples), as prediction candidates, and the threepieces of motion information may be represented by A0, A1, and A2,respectively. In case where a width and a height of the current blockare W and H, respectively, and coordinates of a top-left sample positionof the current block is (xp, yp), A0 may represent a motion vector of asample of (xp−1, yp−1) coordinates, A1 may represent a motion vector ofa sample of (xp, yp−1) coordinates, and A2 may represent a motion vectorof a sample of (xp−1, yp) coordinates, In this case, the encoding devicemay use at least one of the motion vectors A0, A1 and A2 as a predictioncandidate of v0. That is, the encoding device may derive the motionvector v0 regarding CP0 based on the neighboring sample group 0including at least one of the sample of the (xp−1, yp−1) coordinates,the sample of the (xp, yp−1) coordinates, and the sample of the (xp−1,yp) coordinates.

Also, in the case of the motion vector v1 of CP1, the encoding devicemay use two pieces of motion information, among pieces of motioninformation of neighboring blocks (or neighboring samples), asprediction candidates, and the two pieces of motion information may berepresented by B0 and B1. In case where a width and a height of thecurrent block are W and H, respectively, and coordinates of a top-leftsample position of the current block is (xp, yp), B0 may represent amotion vector of a sample of (xp+W, yp−1) coordinates and B1 mayrepresent a motion vector of a sample of (xp+W−1, yp−1) coordinates. Inthis case, the encoding device may use at least one of the motionvectors B0 and B1 as a prediction candidate of v1. That is, the encodingdevice may derive the motion vector v1 regarding CP1 based on theneighboring sample group 1 including the sample of the (xp+W, yp−1)coordinates and the sample of the (xp+W−1, yp−1) coordinates,

Also, in the case of the motion vector v2 of CP2, the encoding devicemay use two pieces of motion information, among pieces of motioninformation of neighboring blocks (or neighboring samples), asprediction candidates, and the two pieces of motion information may berepresented by C0 and C1. In case wherea width and a height of thecurrent block are W and H, respectively, and coordinates of a top-leftsample position of the current block is (xp, yp), C0 may represent amotion vector of a sample of (xp−1, yp+H) coordinates and C1 mayrepresent a motion vector of a sample of (xp−1, yp+H−1) coordinates. Inthis case, the encoding device may use at least one of the motionvectors C0 and C1 as a prediction candidate of v2. That is, the encodingdevice may derive the motion vector v2 regarding CP2 based on theneighboring sample group 2 including the sample of the (xp−1, yp+H)coordinates and the sample of the (xp−1, yp+H−1) coordinates.

Also, in case where a partition ID of the current block is 1, theencoding device may further include samples of neighboring blocks of thecurrent CU as prediction candidates for the motion vector 0 of CP0 andthe motion vector v2 of CP2. For example, in the case of the motionvector v0 of CP0, the encoding device may further include motioninformation of neighboring blocks (i.e., neighboring samples) as aprediction candidate. In detail, the encoding device may further use atleast one of two pieces of motion information of neighboring samples asa prediction candidate, and the two pieces of motion information may berepresented by A3 and A4, respectively. In case where a width and aheight of the CU including the current block are H and coordinates ofthe top-left sample position of the CU is (xc, yc), A3 may represent amotion vector of a sample of (xc−1, yc−1) coordinates and A4 mayrepresent a motion vector of a sample of (xc−1, yc) coordinates. In thiscase, the encoding device may further use at least one of the motionvectors A3 and A4 as a prediction candidate of v0. That is, the encodingdevice may further include at least one of the sample of the (xc−1,yc−1) coordinates, the sample of the (xc−1, yc) coordinates, and thesample of the (xc, yc−1) coordinates in the neighboring sample group 0.

Also, in the case of the motion vector v2 of CP2, the encoding devicemay further include motion information of neighboring blocks (i.e.,neighboring samples) as a prediction candidate. In detail, the encodingdevice may further use at least one of two pieces of motion informationof neighboring samples as a prediction candidate, and the two pieces ofmotion information may be represented by C2 and C3, respectively. Incase where a width and a height of the CU including the current blockare H and coordinates of the top-left sample position of the CU is (xc,yc), C2 may represent a motion vector of a sample of (xc−1, ye+H)coordinates and C3 may represent a motion vector of a sample of (xc−1,yc+H−1) coordinates. In this case, the encoding device may further useat least one of the motion vectors C2 and. C3 as a prediction candidateof v2. That is, the encoding device may further include at least one ofthe sample of the (xc−1, y c+11) coordinates and the sample of the(xc−1, yc+H−1) coordinates in the neighboring sample group 2.

In another example, in case where the current block is a PU to which thepartitioning type nR×2N is applied, for example, in the case of themotion vector v0 of CP0, the encoding device may use three pieces ofmotion information, among pieces of motion information of neighboringblocks (or neighboring samples), as prediction candidates, and the threepieces of motion information may be represented by A0, A1, and A2,respectively. In case where a width and a height of the current blockare W and H, respectively, and coordinates of a top-left sample positionof the current block is (xp, yp), A0 may represent a motion vector of asample of (xp−1, yp−1) coordinates, A1 may represent a motion vector ofa sample of (xp, yp−1) coordinates, and A2 may represent a motion vectorof a sample of (xp−1, yp) coordinates. In this case, the encoding devicemay use at least one of the motion vectors A0, A1 and A2 as a predictioncandidate of v0. That is, the encoding device may derive the motionvector v0 regarding CP0 based on the neighboring sample group 0sincluding at least one of the sample of the (xp−1, yp−1) coordinates,the sample of the (xp, yp−1) coordinates, and the sample of the (xp−1,yp) coordinates.

Also, in the case of the motion vector v1 of CP1, the encoding devicemay use two pieces of motion information, among pieces of motioninformation of neighboring blocks (or neighboring samples), asprediction candidates, and the two pieces of motion information may berepresented by B0 and B1. In case wherea width and a height of thecurrent block are W and H, respectively, and coordinates of a top-leftsample position of the current block is (xp, yp), B0 may represent amotion vector of a sample of (xp+W, yp−1) coordinates and B1 mayrepresent a motion vector of a sample of (xp+W−1, yp−1) coordinates. inthis case, the encoding device may use at least one of the motionvectors B0 and B1 as a prediction candidate of v1. That is, the encodingdevice may derive the motion vector v1 regarding CP1 based on theneighboring sample group 1 including the sample of the (xp+W, yp−1)coordinates and the sample of the (xp+W−1, yp−1) coordinates,

Also, in the case of the motion vector v2 of CP2, the encoding devicemay use two pieces of motion information, among pieces of motioninformation of neighboring blocks (or neighboring samples), asprediction candidates, and the two pieces of motion information may berepresented by C0 and C1. In case wherea width and a height of thecurrent block are W and H, respectively, and coordinates of a top-leftsample position of the current block is (xp, yp), C0 may represent amotion vector of a sample of (xp−1, yp+H) coordinates and C1 mayrepresent a motion vector of a sample of (xp−1, yp+H−1) coordinates. Inthis case, the encoding device may use at least one of the motionvectors C0 and C1 as a prediction candidate of v2. That is, the encodingdevice may derive the motion vector v2 regarding CP2 based on theneighboring sample group 2 including the sample of the (xp−1, yp+H)coordinates and the sample of the (xp−1, yp+H−1) coordinates.

Also, in case where a partition ID of the current block is 1, theencoding device may further include samples of neighboring blocks of thecurrent CU as prediction candidates for the motion vector v0 of CP0 andthe motion vector v2 of CP2. For example, in the case of the motionvector v0 of CP0, the encoding device may further include motioninformation of nei ghboring blocks (i.e., neighboring samples) as aprediction candidate. In detail, the encoding device may further use atleast one of three pieces of motion information of neighboring samplesas a prediction candidate, and the three pieces of motion informationmay be represented by A3, A4, and A5, respectively. In case where awidth and a height of the CU including the current block are H andcoordinates of the top-left sample position of the CU is (xc, yc), A3may represent a motion vector of a sample of (xc−1, yc−1) coordinates,A4 may represent a motion vector of a sample of (xc, yc−1) coordinates,and A5 may represent a motion vector of a sample of (xc−1, yc)coordinates. In this case, the encoding device may further use at leastone of the motion vectors A3, A4, and A5 as a prediction candidate ofv0. That is, the encoding device may further include at least one of thesample of the xc−1, yc−1) coordinates, the sample of the (xc−1, xc)coordinates, and the sample of the (xc yc−1) coordinates in theneighboring sample group 0.

Also, in the case of the motion vector v2 of CP2, the encoding devicemay further include motion information of neighboring blocks (i.e.,neighboring samples) as a prediction candidate. In detail, the encodingdevice may further use at least one of three pieces of motioninformation of neighboring samples as a prediction candidate, and thethree pieces of motion information may be represented by C2, C3, and C4,respectively. In case where a width and a height of the CU including lecurrent block are H and coordinates of the top-left sample position ofthe CU is (xc, yc), C2 may represent a motion vector of a sample of(xc−1, yc+H) coordinates, C3 may represent a motion vector of a sampleof (xc, yc+H.) coordinates, and C4 may represent a motion vector of asample of (xc−1, yc+H−1) coordinates. In this case, the encoding devicemay further use at least one of the motion vectors C2, C3, and C4 as aprediction candidate of v2. That is, the encoding device may furtherinclude at least one of the sample of the (xc−1, yc+H−1) coordinates,the sample of the (xc, yc+H) coordinates, and the sample of the (xc−1,yc+H−1) coordinates in the neighboring sample group 2.

In another example, in case where the current block is a PU to which thepartitioning type 2N×nU is applied, for example, in the case of themotion vector v0 of CP0, the encoding device may use three pieces ofmotion information, among pieces of motion information of neighboringblocks (or neighboring samples), as prediction candidates, and the threepieces of motion information may be represented by A0, A1, and A2,respectively. In case where a width and a height of the current blockare W and H, respectively, and coordinates of a top-left sample positionof the current block is (xp, yp), A0 may represent a motion vector of asample of (xp−1, yp−1) coordinates, A1 may represent a motion vector ofa sample of (xp, yp−1) coordinates, and A2 may represent a motion vectorof a sample of (xp−1, yp) coordinates. In this case, the encoding devicemay use at least one of the motion vectors A0, A1 and A2 as a predictioncandidate of v0. That is, the encoding device may derive the motionvector v0 regarding CP0 based on the neighboring sample group 0including at least one of the sample of the (xp−1, yp−1) coordinates,the sample of the (xp, yp−1) coordinates, and the sample of the (xp−1,yp) coordinates.

Also, in the case of the motion vector v1 of CP1, the encoding devicemay use two pieces of motion information, among pieces of motioninformation of neighboring blocks (or neighboring samples), asprediction candidates, and the two pieces of motion information may berepresented by B0 and B1 .In case wherea width and a height of thecurrent block are W and H, respectively, and coordinates of a top-leftsample position of the current block is (xp, yp), B0 may represent amotion vector of a sample of (xp+W, yp−1) coordinates and B1 mayrepresent a motion vector of a sample of (xp+W−1, yp−1) coordinates. Inthis case, the encoding device may use at least one of the motionvectors B0 and B1 as a prediction candidate of v1. That is, the encodingdevice may derive the motion vector v1 regarding CP1 based on theneighboring sample group 1 including at least one of the sample of the(xp+W, yp−1) coordinates and the sample of the (xp+W−1, yp−1)coordinates.

Also, in the case of the motion vector v2 of CP2, the encoding devicemay use two pieces of motion information, among pieces of motioninformation of neighboring blocks (or neighboring samples), asprediction candidates, and the two pieces of motion information may berepresented by C0 and C1. In case wherea width and a height of thecurrent block are W and H, respectively, and coordinates of a top-leftsample position of the current block is (xp, yp), C0 may represent amotion vector of a sample of (xp−1, yp+H) coordinates and C1 mayrepresent a motion vector of a sample of (xp−1, yp+H−1) coordinates. :Inthis case, the encoding device may use at least one of the motionvectors C0 and C1 as a prediction candidate of v2. That is, the encodingdevice may derive the motion vector v2 regarding CP2 based on theneighboring sample group 2 including at least one of the sample of the(xp−1, yp+H) coordinates and the sample of the (xp−1, yp+H−1)coordinates.

Also, in case where a partition ID of the current block is 1, theencoding device may further include samples of neighboring blocks of thecurrent CU as prediction candidates for the motion vector v0 of CP0 andthe motion vector v1 of CP1. For example, in the case of the motionvector v0 of CP0, the encoding device may further include motioninformation of neighboring blocks (i.e., neighboring samples) as aprediction candidate. In detail, the encoding device may further use atleast one of two pieces of motion information of neighboring samples asa prediction candidate, and the two pieces of motion information may berepresented by A3 and A4, respectively. In case where a width and aheight of the CU including the current block are W and coordinates ofthe top-left sample position of the CU is (xc, yc), A3 may represent amotion vector of a sample of (xc−1, yc−1) coordinates and A4 mayrepresent a motion vector of a sample of (xc, yc−1) coordinates. In thiscase, the encoding device may further use at least one of the motionvectors A3 and A1 as a prediction candidate of v0. That is, the encodingdevice may further include at least one of the sample of the (xc−1,yc−1) coordinates and the sample of the (xc, yc−1) coordinates in theneighboring sample group 0.

Also, in the case of the motion vector v1 of CP1, the encoding devicemay further include motion information of neighboring blocks (i.e.,neighboring samples) as a prediction candidate. In detail, the encodingdevice may further use at least one of two pieces of motion informationof neighboring samples as a prediction candidate, and the two pieces ofmotion information may be represented by B2 and B3, respectively. Incase where a width and a height of the CU including the current blockare W and coordinates of the top-left sample position of the CU is (xc,yc), B2 may represent a motion vector of a sample of (xc+W, yc−1)coordinates and B3 may represent a motion vector of a sample of (xc+W−1,yc−1) coordinates. In this case, the encoding device may further use atleast one of the motion vectors B2 and B3 as a prediction candidate ofv1. That is, the encoding device may further include at least one of thesample of the (xc+W, yc−1) coordinates and the sample of the (xc+W−1,yc−1) coordinates in the neighboring sample group 1.

In another example, in case where the current block is a PU to which thepartitioning type 2N×nD is applied, for example, in the case of themotion vector v0 of CP0, the encoding device may use three pieces ofmotion information, among pieces of motion information of neighboringblocks (or neighboring samples), as prediction candidates, and the threepieces of motion information may be represented by A0, A1, and A2,respectively. In case where a width and a height of the current blockare W and H, respectively, and coordinates of a top-left sample positionof the current block is (xp, yp), A0 may represent a motion vector of asample of (xp−1, yp−1) coordinates, A1 may represent a motion vector ofa sample of (xp, yp−1) coordinates, and A2 may represent a motion vectorof a sample of (xp−1, yp) coordinates. In this case, the encoding devicemay use at least one of the motion vectors A0, A1 and A2 as a predictioncandidate of v0. That is, the encoding device may derive the motionvector v0 regarding CP0 based on the neighboring sample group 0including at least one of the sample of the (xp−1, yp−1) coordinates,the sample of the (xp, yp−1) coordinates, and the sample of the (xp−1,yp) coordinates.

Also, in the case of the motion vector v1 of CP1, the encoding devicemay use two pieces of motion information, among pieces of motioninformation of neighboring blocks (or neighboring samples), asprediction candidates, and the two pieces of motion information may berepresented by B0 and B1. In case where a width and a height of thecurrent block are W and H, respectively, and coordinates of a top-leftsample position of the current block is (xp, yp), B0 may represent amotion vector of a sample of (xp+W, yp−1) coordinates and B1 mayrepresent a motion vector of a sample of (xp+W−1, yp−1) coordinates. Inthis case, the encoding device may use at least one of the motionvectors B0 and B1 as a prediction candidate of v1. That is, the encodingdevice may derive the motion vector v1. regarding CP1 based on theneighboring sample group 1 including at least one of the sample of the(xp+W, yp−1) coordinates and the sample of the (xp+W−1, yp−1)coordinates.

Also, in the case of the motion vector v2 of CP2, the encoding devicemay use two pieces of motion information, among pieces of motioninformation of neighboring blocks (or neighboring samples), asprediction candidates, and the two pieces of motion information may berepresented by C0 and C1. In case where a width and a height of thecurrent block are W and H, respectively, and coordinates of a top-leftsample position of the current block is (xp, yp), C0 may represent amotion vector of a. sample of (xp−1, yp+H) coordinates and C1 mayrepresent a motion vector of a sample of (xp−1, yp+H−1) coordinates. Inthis case, the encoding device may use at least one of the motionvectors C0 and C1 as a prediction candidate of v2. That is, the encodingdevice may derive the motion vector v2 regarding CP2 based on theneighboring sample group 2 including at least one of the sample of the(xp−1, yp+H) coordinates and the sample of the (xp−1, yp+H−1)coordinates.

Also, in case where a partition ID of the current block is 1, theencoding device may further include samples of neighboring blocks of thecurrent CU as prediction candidates for the motion vector v0 of CP0 andthe motion vector v1 of CP1. For example, in the case of the motionvector v0 of CP0, the encoding device may further include motioninformation of neighboring blocks (i.e., neighboring samples) as aprediction candidate. In detail, the encoding device may further use atleast one of three pieces of motion information of neighboring samplesas a prediction candidate, and the three pieces of motion informationmay be represented by A3, A4, and AS, respectively. In case where awidth and a height of the CU including the current block are W andcoordinates of the top-left sample position of the CU is (xc, yc), A3may represent a motion vector of a sample of (xc−1, yc) coordinates, 44may represent a motion vector of a sample of (xc−1, yc−1) coordinates,and AS may represent a motion vector of a sample of (xc, yc−1)coordinates. In this case, the encoding device may further use at leastone of the motion vectors A3, A4, and A5 as a prediction candidate ofv0. That is, the encoding device may further include at least one of thesample of the (xc−1, yc−1) coordinates, the sample of the (xc−1, yc)coordinates, and the sample of the (xc, yc−1) coordinates in theneighboring sample group 0.

Also, in the case of the motion vector v1 of CP1, the encoding devicemay further include motion information of neighboring blocks (i.e.,neighboring samples) as a prediction candidate. In detail, the encodingdevice may further use at least one of three pieces of motioninformation of neighboring samples as a prediction candidate, and thethree pieces of motion information may be represented by B2, B3, and B4,respectively. In case where a width and a height of the CU including thecurrent block are W and coordinates of the top-left sample position ofthe CU is (xc, yc), B2 may represent a motion vector of a sample of(xc+W, yc) coordinates, B3 may represent a. motion vector of a sample of(xc+W, yc−1) candidates, and B4 may represent a motion vector of asample of (xc+W−1, yc−1) coordinates. In this case, the encoding devicemay further use at least one of the motion vectors B2, B3, and B4 as aprediction candidate of v1. That is, the encoding device may furtherinclude at least one of the sample of the (xc+W, yc) coordinates, thesample of the (xc+W, yc−1) coordinates, and the sample of the (xc+W−1,yc−1) coordinates in the neighboring sample group 1.

In another example, the encoding device may use the same predictioncandidates of PUs included in the CU may use the same predictioncandidates of the PUs in the CU as prediction candidates for the motionvectors of the CPs, regardless of partition ID. For example, in the caseof the motion vector v0 of CP0 of the current block, the encoding devicemay use three pieces of motion information, among pieces of motioninformation of neighboring blocks (i.e., neighboring blocks orneighboring samples of the current CU), as prediction candidates, andthe three pieces of motion information may be represented by A0, A1, andA2, respectively. In case where a width and a height of the CU are W andrespectively, and coordinates of the top-left sample position of the CUis (xc, yc), A0 may represent a motion vector of a sample of (xc−1,yc−1) coordinates, A1 may represent a motion vector of a sample of (xc,yc−1) coordinates, and A2 may represent a motion vector of a sample of(xc−1, yc) coordinates. In this case, the encoding device may use atleast one of the motion vectors A0, A1 and A2 as a prediction candidateof v0.

Also, in the case of the motion vector v1 of CP1 of the current block,the encoding device may use two pieces of motion information, amongpieces of motion information of neighboring blocks (or neighboringsamples), as prediction candidates, and the two pieces of motioninformation may be represented by B0 and B1. In case where a width and aheight of the CU are W and coordinates of the top-left sample positionof the CU is (xc, yc), B0 may represent a motion vector of a sample of(xc+W, yc−1) coordinates and B1 may represent a motion vector of asample of (xc+W−1, yc−1) coordinates. In this case, the encodin devicemay use at least one of the motion vectors B0 and B1 as a predictioncandidate of v1.

Also, in the case of the motion vector v2 of CP2 of the current block,the encoding device may use two pieces of motion information, amongpieces of the motion information of the neighboring blocks (orneighboring samples), as prediction candidates, and the two pieces ofmotion information may be represented by C0 and C1, respectively. Incase where a width and a height of the CU are W and coordinates of thetop-left sample position of the CU is (xc, yc), C0 may represent amotion vector of a sample of (xc−1, yc+H) coordinates and C1 mayrepresent a motion vector of a sample of (xc−1, yc+H−1) coordinates. Inthis case, theencoding device may use at least one of the motion vectorsC0 and C1 as a prediction candidate of v2.

In another example, as a method of configuring a prediction candidatefor motion vectors of CPs of a PU to which the nL×2N, nR×2N, 2N×nU, or2N×nD partitioning type is applied, prediction candidates may be limitedto a predetermined number so as to be configured.

In another example, in case where the current block is a PU to which thepartitioning type nL×2N, nR×2N, 2N×nU, or 2N×nD is applied, the encodingdevice may configure the prediction candidates of each CP by limitingthe number thereof into two. For example, in the case of the motionvector v0 of CP0, the encoding device may use two pieces of motioninformation, among pieces of motion information of the neighboringblocks (or neighboring samples), as prediction candidates, and the twopieces of motion information may be represented by A0 and A1. In casewhere a width and a height of the current block are W and H,respectively, and the coordinates of the top-left sample position of thecurrent block is (xp, yp), A0 may represent a motion vector of a sampleof (xp−1, yp−1) coordinates and A1 may represent a motion vector of asample of (xp, vp−1) coordinates. In this case, the encoding device mayuse A0 and A1 as prediction candidates of v0. That is, the encodingdevice may include the sample of the (xp−1, yp−1) coordinates and thesample of the (xp, yp−1) coordinates in the neighboring sample group 0,and availability of the sample of the (xp−1, yp−1) coordinates and thesample of the (xp, yp−1) coordinates may be sequentially determinedaccording to first predefined priority order.

Also, in the case of the motion vector v1 of CP1, the encoding devicemay use two pieces of motion information, among pieces of motioninformation of the neighboring blocks (or neighboring samples), asprediction candidates, and the two pieces of motion information may berepresented by B0 and B1. In case where a width and a height of thecurrent block are W and H, respectively, and the coordinates of thetop-left sample position of the current block is (xp, yp), B0 mayrepresent a motion vector of a sample of (xp+W, yp−1) coordinates and B1may represent a motion vector of a. sample of (xp+W−1, yp−1)coordinates. In this case, the encoding device may use B0 and B1 asprediction candidates of v1. That is, the encoding device may includethe sample of the (xp+W, yp−1) coordinates and the sample of the(xp+W−1, yp−1) coordinates in the neighboring sample group 1, andavailability of the sample of the (xp+W, yp−1) coordinates and thesample of the (xp+W−1, yp−1) coordinates may be sequentially determinedaccording to second predefined priority order.

Also, in the case of the motion vector v2 of CP2, the encoding devicemay use two pieces of motion information, among pieces of motioninformation of the neighboring blocks (or neighboring samples), asprediction candidates, and the two pieces of motion information may berepresented by C0 and C1. In case where a width and a height of thecurrent block are W and. H, respectively, and the coordinates of thetop-left sample position of the current block is (xp, yp), C0 mayrepresent a motion vector of a sample of (xp−1, yp+H) coordinates and C1may represent a motion vector of a sample of (xp−1, yp+H−1) coordinates.In this case, the encoding device may use C0 and C1 as predictioncandidates of v2. That is, the encoding device may include the sample ofthe (xp−1, yp+H) coordinates and the sample of the xp−1, yp+H−1)coordinates in the neighboring sample group 2, and availability of thesample of the (xp−1, yp+H) coordinates and the sample of the (xp−1,yp+H−1) coordinates may be sequentially determined according to thirdpredefined priority order.

The encoding device derives a sample unit motion vector in the currentblock based on motion vectors for the CPs (S1920). According to theaffine motion model, motion vectors may be different according to eachsample coordinate in the current block. If a motion vector of CP0, amotion vector of CP1, and a motion vector of CP2 are known, a motionvector according to a sample position in the current block may bederived. That is, according to the affine motion model, the sample unitmotion vector of the sample position may be derived using the motionvectors in the CPs, the motion vector (v_(x0), v_(y0)) of CP0, themotion vector (v_(x1), v_(y1)) of CP1, and the motion vector (v_(x2),v_(y2)) based on distance ratios between the coordinates (x, y) andthree control points. In this case, the encoding device may derive thesample unit motion vector of the sample position in the current blockbased on Equations 2 to 5 described above.

The encoding device generates a prediction sample for the current blockbased on the sample unit motion vector (S1930). The encoding device mayderive a reference region in a reference picture based on the sampleunit motion vector and generate a prediction sample of the current blockbased on the reconstructed sample in the reference region. if aprediction mode for the current block is not a skip mode, the encodingdevice may generate a residual sample (or residual signal) based on theoriginal sample of original picture and the prediction sample.

The encoding device encodes the prediction mode information for thecurrent block and outputs the encoded information (S1940). The encodingdevice may encode the prediction mode for the current block and thederived motion vector and output the encoded information in the form ofa bit stream. Also, when the CP of a previous block to be decoded hasthe same position as the CP of the current block, the encoding devicemay not separately code the motion information on the CP of the currentblock.

For example, in the case of the motion information for CP0 of thecurrent block, in case where an uppermost block, among left neighboringblocks adjacent to a left boundary of the current block, is decodedbased on the affine motion model, a motion vector of CP1 of thecorresponding block may be used as a motion vector of CP0 of the currentblock, and thus, motion information for CP0 may not be separately coded.Also, in case where a leftmost block, among upper neighboring blocksadjacent to an upper boundary of the current block, is decoded based onthe affine motion model, a motion vector of CP2 of the correspondingblock may be used as a motion vector of CP0 of the current block, andthus, motion information for CP0 may not be separately coded. Also, incase where an upper left neighboring block of the current block isdecoded based on the affine motion model, a motion vector of a lowerright neighboring sample of the corresponding block derived based on theCPs of the corresponding block may be used as a motion vector of CP0 ofthe current block, and thus, motion information for CP0 may not beseparately coded. In this case, the motion vector of the lower rightneighboring sample of the corresponding block may be derived based onthe CPs of the corresponding block based on Equations 2 to 5 describedabove.

For example, in the case of CP1 of the current block, in case where anupper right neighboring block of the current block is decoded based onthe affine motion model, a motion vector of CP2 of the correspondingblock may be used as a motion vector of CP1 of the current block, andthus, motion information for CP0 may not be separately coded. Also, incase where a rightmost block of the upper neighboring blocks adjacent tothe upper boundary of the current block is decoded based on the affinemotion model, a motion vector of a lower right neighboring sample of thecorresponding block derived based on the CPs of the block may be used asa motion vector of CPI of the current block, and thus, motioninformation for CP0 may not be separately coded. In this case, themotion vector of the lower right neighboring samples of thecorresponding block may be derived based on the CPs of the correspondingblock based on Equations 2 to 5 described above

For example, in the case of CP2 of the current block, in case where alower left neighboring block of the current block is decoded based onthe affine motion model, a motion vector of CP1 of the correspondingblock may be used as a motion vector of CP2 of the current block, andthus, motion information for CP0 may not be separately coded. Also, incase where a lowermost block of left neighboring blocks adjacent to aleft boundary of the current block is decoded based on the affine motionmodel, a motion vector of a lower right neighboring sample of thecorresponding block derived based on the CPs of the current block may beused as a motion vector of CP2 of the current block, and thus, motioninformation for CP0 may not be separately coded.

The bit stream may be transmitted to a decoding device through a networkor a storage medium.

Although not shown, the encoding device may encode information onresidual samples of the current block and output the same. Theinformation on the residual samples may include transform coefficientsrelating to the residual samples.

FIG. 20 schematically illustrates a video decoding method by a decodingdevice according to the present invention. The method disclosed in FIG.20 may be performed by the decoding device disclosed in FIG. 2 .Specifically, for example, steps S2000 to S2030 of FIG. 20 may beperformed by the predicting unit of the decoding device.

The decoding device derives control points (CPs) for the current block(S2000). The decoding device may receive information on inter-predictionof the current block through a bit stream. In case where the affinemotion model is applied to the current block, the decoding device mayderive CPs to apply the affine motion model. The CPs may be three CPs.For example, in case where the current block is a PU partitioned from aCU based on the partitioning type 2N×2N and a width and a height of thecurrent block are S, the decoding device may derive three CPs in whichCP0 is a sample of (0, 0) coordinates, CP1 is a sample of (S, 0)coordinates, and CP2 is a sample of (0, S) coordinates based oncoordinates (0, 0) of the top-left sample position of the current block.

Also, in case where the current block is a PU partitioned from a CUbased on the partitioning type N×2N and a width and a height of thecurrent block are S/2 and S, respectively, the decoding device mayderive three CPs in which CP0 is a sample of (0, 0) coordinates, CP1 isa sample of (S/2, 0) coordinates, and CP2 is a sample of (0, S)coordinates based on the coordinates (0, 0) of the top-left sampleposition of the current block.

Also, in case where the current block is a PU partitioned from a CUbased on the partitioning type 2N×N and a width and a height of thecurrent block are S and S/2, respectively, the decoding device mayderive three CPs in which CP0 is a sample of (0, 0) coordinates, CP1 isa sample of (S/2, 0) coordinates, and CP2 is a sample of (0, S/2)coordinates based on the coordinates (0, 0) of the top-left sampleposition of the current block.

Also, in case where the current block is a PU partitioned from a CUbased on the partitioning type nL×2N, nR×2N, 2N×nU, or 2N×nD and a widthand a height of the current block are W and H, respectively, thedecoding device may derive three CPs in which CP0 is a sample of (0, 0)coordinates, CP1 is a sample of (W, 0) coordinates, and CP2 is a sampleof (0, H) coordinates based on the coordinates (0, 0) of the top-leftsample position of the current block.

The decoding device Obtains motion vectors for the CPs (S2010).

The decoding device may derive motion vectors of the CPs based on amotion vector for the current block and a motion vector of a neighboringblock of the current block. The decoding device may receive motioninformation of the CPs through a bit stream. In case where a motionvector for a CP which is the same in position as that of a CP of thecurrent block is derived before the current block is decoded, thedecoding device may not receive information regarding the CP of thecurrent block. The decoding device may configure adjacent samples ofeach CP as a neighboring sample group and derive a motion vector of theCP based on the neighboring sample group. The neighboring sample groupmay be determined based on a partitioning type, a partition ID, and ashape of the current block.

For example, in case where the current block is a PU to which thepartitioning type 2N×2N is applied, in the case of the motion vector v0of CP0, the decoding device may use three pieces of motion information,among pieces of motion information of neighboring blocks (or neighboringsamples), as prediction candidates, and the three pieces of motioninformation may be represented by A0, A1, and A2, respectively. In casewhere a width and a height of the current block are S and coordinates ofatop-left sample position of the current block is (xp, yp), A0 mayrepresent a motion vector of a sample of (xp−1, yp−1) coordinates, A1may represent a motion vector of a sample of (xp, yp−1) coordinates, andA2 may represent a motion vector of a sample of (xp−1, yp) coordinates.In this case, the decoding device may use at least one of the motionvectors A0, A1 and A2 as a prediction candidate of v0. That is, thedecoding device may derive the motion vector v0 regarding CP0 based on aneighboring sample group 0 including the sample of the (xp−1, yp−1)coordinates, the sample of the (xp, yp−1) coordinates, and the sample ofthe (xp−1, yp) coordinates.

Also, in the case of the motion vector v1 of CP1, the decoding devicemay use two pieces of motion information, among pieces of motioninformation of neighboring blocks (or neighboring samples), asprediction candidates, and the two pieces of motion information may berepresented by B0 and B1. In case where a width and a height of thecurrent block are S and coordinates of a top-left sample position of thecurrent block is (xp, yp), B0 may represent a motion vector of a. sampleof (xp+S, yp−1) coordinates and B1 may represent a motion vector of asample of (xp+S−1, yp−1) coordinates. In this case, the decoding devicemay use at least one of the motion vectors B0 and B1 as a predictioncandidate of v1. That is, the decoding device may derive the motionvector v1 regarding CP1 based on a neighboring sample group 1 includingthe sample of the (xp+S, yp−1) coordinates and the sample of the(xp±S−1, yp−1) coordinates.

Also, in the case of the motion vector v2 of CP2, the decoding devicemay use two pieces of motion information, among pieces of motioninformation of neighboring blocks (or neighboring samples), asprediction candidates, and the two pieces of motion information may berepresented by C0 and C1. In case where a width and a height of thecurrent block are S and coordinates of a top-left sample position of thecurrent block is (xp, yp), C0 may represent a motion vector of a sampleof (xp−1, yp+S) coordinates and C1 may represent a motion vector of asample of (xp−1, yp+S−1) coordinates. In this case, the decoding devicemay use at least one of the motion vectors C0 and C1 as a predictioncandidate of v2. That is, the decoding device may derive the motionvector v2 regarding CP2 based on a neighboring sample group 2 includingat least one of the sample of the (xp−1, yp+S) coordinates and thesample of the (xp−1, yp+S−1) coordinates.

In another example, in case where the current block is a PU to which thepartitioning type 2N×N is applied, in the case of the motion vector v0of CP0, the decoding device may use three pieces of motion information,among pieces of motion information of neighboring blocks (or neighboringsamples), as prediction candidates, and the three pieces of motioninformation may be represented by A0, A1, and A2, respectively. In casewhere a width and a height of the current block are S and S/2,respectively, and coordinates of a top-left sample position of thecurrent block is (xp, yp), A0 may represent a motion vector of a sampleof (xp−1, yp−1) coordinates, A1 may represent a motion vector of asample of (xp, yp−1) coordinates, and A2 may represent a motion vectorof a sample of (xp−1, yp) coordinates. In this case, the decoding devicemay use at least one of the motion vectors A0, A1 and A2 as a predictioncandidate of v0. That is, the decoding device may derive the motionvector v0 regarding CP0 based on a neighboring sample group 0 includingat least one of the sample of the (xp−1, yp−1) coordinates, the sampleof the (xp, yp−1) coordinates, and the sample of the (xp−1, yp)coordinates.

Also, in the case of the motion vector v1 of CP1, the decoding devicemay use two pieces of motion information, among pieces of motioninformation of neighboring blocks (or neighboring samples), asprediction candidates, and the two pieces of motion information may berepresented by B0 and B1. In case where a width and a height of thecurrent block are S and S/2, respectively, and coordinates of a top-leftsample position of the current block is (xp, yp), B0 may represent amotion vector of a sample of (xp+S, yp−1) coordinates and B1 mayrepresent a motion vector of a sample of (xp+S−1, yp−1) coordinates. Inthis case, the decoding device may use at least one of the motionvectors B0 and B1 as a prediction candidate of v1. That is, the decodingdevice may derive the motion vector v1. regarding CP1 based on aneighboring sample group 1 including at least one of the sample of the(xp+S, yp−1) coordinates and the sample of the (xp+S−1, yp−1)coordinates.

Also, in the case of the motion vector v2 of CP2, the decoding devicemay use two pieces of motion information, among pieces of motioninformation of neighboring blocks (or neighboring samples), asprediction candidates, and the two pieces of motion information may berepresented by C0 and C1. In case where a width and a height of thecurrent block are S and S/2, respectively, and coordinates of a top-leftsample position of the current block is (xp, yp), C0 may represent amotion vector of a sample of (xp−1, yp+S/2) coordinates and C1 mayrepresent a motion vector of a sample of (xp−1, yp+S/2−1) coordinates.In this case, the decoding device may use at least one of the motionvectors C0 and C1 as a prediction candidate of v2. That is, the decodingdevice may derive the motion vector v2 regarding CP2 based on aneighboring sample group 2 including at least one of the sample of the(xp−1, yp+S/2) coordinates and the sample of the (xp−1, yp+S/2−1)coordinates.

In case where a partition ID of the current block is 1, the decodingdevice may further include samples of neighboring blocks of the currentCU as prediction candidates for the motion vector v0 of CP0 and themotion vector v1 of CP1. For example, in the case of the motion vectorv0 of CP0, the decoding device may further include motion information ofneighboring blocks (i.e., neighboring samples) as a predictioncandidate. In detail, the decoding device may further use at least oneof three pieces of motion information of neighboring samples as aprediction candidate, and the three pieces of motion information may berepresented by A3, A4, and A5, respectively. In ease where a width and aheight of the CU including the current block are S and coordinates ofthe top-left sample position of the CU is (xc, yc), A3 may represent amotion vector of a sample of (xc−1, yc) coordinates, A4 may represent amotion vector of a sample of (xc−1, yc−1) coordinates, and A5 mayrepresent a motion vector of a sample of (xc, yc−1) coordinates. In thiscase, the decoding device may further use at least one of the motionvectors A3, A4, and A5 as a prediction candidate of v0. That is, thedecoding device may further include at least one of the sample of the(xc−1, yc−1) coordinates, the sample of the (xc−1, yc) coordinates, andthe sample of the (xc, yc−1) coordinates in the neighboring sample group0.

Also, in the case of the motion vector v1 of CP1, the decoding devicemay further include motion information of neighboring blocks (orneighboring samples) as a prediction candidate. In detail, the decodingdevice may further use at least one of three pieces of motioninformation of neighboring samples as a prediction candidate, and thethree pieces of motion information may be represented by B2, B3, and B4,respectively. In ease where a width and a height of the CU including thecurrent block are S and coordinates of the top-lett sample position ofthe CU is (xc, ye), B2 may represent a motion vector of a sample of(xc+S, yc) coordinates, B3 may represent a. motion vector of a sample of(xc+S, yc−1) coordinates, and B4 may represent a motion vector of asample of (xc+S−1, yc−1) coordinates. In this case, the decoding devicemay further use at least one of the motion vectors B2, B3, and B4 as aprediction candidate of v1. That is, the decoding device may furtherinclude at least one of the sample of the (xc+S, yc) coordinates, thesample of the (xc+S, yc−1) coordinates, and the sample of the (xc+S−1,yc−1) coordinates in the neighboring sample group 1.

Also, the decoding device may configure the prediction candidates forthe motion vectors of the CPs of the current block by limiting thenumber of prediction candidates to a certain number. In the case of themotion vector v0 of CP0, the decoding device may use two pieces ofmotion information, among pieces of motion information of theneighboring blocks (or neighboring samples), as prediction candidates,and the two pieces of motion information may be represented by A0 andA1. In case where a width and a height of the current block are S andS/2, respectively, and the coordinates of the top-left sample positionof the current block is (xp, yp), A0 may represent a motion vector of asample of (xp−1, yp−1) coordinates and A1 may represent a motion vectorof a sample of (xp, yp−1) coordinates. In this case, the decoding devicemay use A0 and A1 as prediction candidates of v0. That is, the decodingdevice may include the sample of the (xp−1, yp−1) coordinates and thesample of the (xp, yp−1) coordinates in the neighboring sample group 0,and availability of the sample of the (xp−1, yp−1) coordinates and thesample of the (xp, yp−1) coordinates may be sequentially determinedaccording to first predefined priority order.

In the case of the motion vector v1 of CP1, the decoding device may usetwo pieces of motion information, among pieces of motion information ofthe neighboring blocks (or neighboring samples), as predictioncandidates, and the two pieces of motion information may be representedby B0 and B1. In case where a width and a height of the current blockare S and S12, respectively, and the coordinates of the top-left sampleposition of the current block is (xp, yp), B0 may represent a motionvector of a sample of (xp+S, yp−1) coordinates and B1 may represent amotion vector of a sample of (xp+S−1, yp−1) coordinates. In this case,the decoding device may use B0 and B1 as prediction candidates ofv1.That is, the decoding device may include the sample of the (xp+S,yp−1) coordinates and the sample of the (xp+S−1, yp−1) coordinates inthe neighboring sample group 1, and availability of the sample of the(xp+S, yp−1) coordinates and the sample of the (xp+S−1, yp−1)coordinates may be sequentially determined according to secondpredefined priority order.

In the case of the motion vector v2 of CP2, the decoding device may usetwo pieces of motion information, among pieces of motion information ofthe neighboring blocks (or neighboring samples), as predictioncandidates, and the two pieces of motion information may be representedby C0 and C1. in case where a width and a height of the current blockare S and S/2, respectively, and the coordinates of the top-left sampleposition of the current block is (xp, yp), C0 may represent a motionvector of a sample of (xp−1, yp +S/2) coordinates and C1 may represent amotion vector of a sample of (xp−1, yp+S/2−1) coordinates. In this case,the decoding device may use C0 and C1 as prediction candidates of v2.That is, the decoding device may include the sample of the (xp−1,yp+S/2) coordinates and the sample of the (xp−1, yp+S/2−1) coordinatesin the neighboring sample group 2, and availability of the sample of the(xp−1, yp+S/2) coordinates and the sample of the (xp−1, yp+S/2−1)coordinates may be sequentially determined according to third predefinedpriority order.

In another example, in case wherethe current block is a PU to which thepartitioning type N×2N is applied, in the case of the motion vector v0of CP0, the decoding device may use three pieces of motion information,among pieces of motion information of neighboring blocks (or neighboringsamples), as prediction candidates, and the three pieces of motioninformation may be represented by A0, A1, and A2, respectively. In casewhere a width and a height of the current block are S/2 and S,respectively, and coordinates of a top-left sample position of thecurrent block is (xp, yp), A0 may represent a motion vector of a sampleof (xp−1, yp−1) coordinates, A1 may represent a motion vector of asample of (xp, yp−1) coordinates, and A2 may represent a motion vectorof a sample of (xp−1, yp) coordinates. In this case, the decoding devicemay use at least one of the motion vectors A0, A1 and A2 as a predictioncandidate of v0. That is, the decoding device may derive the motionvector v0 regarding CP0 based on a neighboring sample group 0 includingthe sample of the (xp−1, yp−1) coordinates, the sample of the (xp, yp−1)coordinates, and the sample of the (xp−1, yp) coordinates.

Also, in the case of the motion vector v1 of CP1, the decoding devicemay use two pieces of motion information, among pieces of motioninformation of neighboring blocks (or neighboring samples), asprediction candidates, and the two pieces of motion information may berepresented by B0 and B1. In case where a width and a height of thecurrent block are S/2 and S, respectively, and coordinates of a top-leftsample position of the current block is (xp, yp), B0 may represent amotion vector of a sample of (xp+S/2, yp−1) coordinates and B1 mayrepresent a motion vector of a sample of (xp+S/2−1, yp−1) coordinates.In this case, the decoding device may use at least one of the motionvectors B0 and B1 as a prediction candidate of v1. Also, in case where apartition ID of the current block is 0, the decoding device may furtherinclude at least one of the motion vector B2 of the sample of the(xp+S/2+1, yp−1) coordinates and the motion vector B3 of the sample ofthe (xp+S/2+2, yp−1) coordinates as a prediction candidate of v1. Thatis, the decoding device may derive the motion vector v1 regarding CPIbased on the neighboring sample group 1 including the sample of the(xp+S/2, yp−1) coordinates and the sample of the (xp+S/2−1, yp−1)coordinates.

Also, in the case of the motion vector v2 of CP2, the decoding devicemay use two pieces of motion information, among pieces of motioninformation of neighboring blocks (or neighboring samples), asprediction candidates, and the two pieces of motion information may berepresented by C0 and C1. In case where a width and a height of thecurrent block are S/2 and S, respectively, and coordinates of atop-leftsample position of the current block is (xp, yp), C0 may represent amotion vector of a sample of (xp−1, yp+S) coordinates and C1 mayrepresent a motion vector of a sample of (xp−1, yp+S−1) coordinates. Inthis case, the decoding device may use at least one of the motionvectors C0 and C1 as a prediction candidate of v2. That is, the decodingdevice may derive the motion vector v2 regarding CP2 based on theneighboring sample group 2 including the sample of the (xp−1, yp+S)coordinates and the sample of the (xp−1, yp+S−1) coordinates.

In case where a partition ID of the current block is 1, the decodingdevice may further include samples of neighboring blocks of the currentCU as prediction candidates for the motion vector v0 of CP0 and themotion vector v2 of CP2. For example, in the case of the motion vectorv0 of CP0, the decoding device may further include motion information ofneighboring blocks (i.e., neighboring samples) as a predictioncandidate. In detail, the decoding device may further use at least oneof three pieces of motion information of neighboring samples as aprediction candidate, and the three pieces of motion information may berepresented by A3, A4, and A5, respectively. In case where a width and aheight of the CU including the current block are S and coordinates ofthe top-left sample position of the CU is (xc, yc), A3 may represent amotion vector of a sample of (xc−1, yc−1) coordinates, A4 may representa motion vector of a sample of (xc, yc−1) coordinates, and A5 mayrepresent a motion vector of a sample of (xc−1, yc) coordinates. In thiscase, the decoding device may further use at least one of the motionvectors A3, A4, and A5 as a prediction candidate of v0. That is, thedecoding device may further include at least one of the sample of the(xc−1, yc−1) coordinates, the sample of the (xc−1, yc) coordinates, andthe sample of the (xc, yc−1) coordinates in the neighboring sample group0. 12811 Also, in the case of the motion vector v2 of CP2, the decodingdevice may further include motion information of neighboring blocks (orneighboring samples) as a prediction candidate. In detail, the decodingdevice may further use at least one of three pieces of motioninformation of neighboring samples as a prediction candidate, and thethree pieces of motion information may be represented by C3, and C4,respectively. In case where a width and a height of the CU including thecurrent block are S and coordinates of the top-left sample position ofthe CU is (xc, ye), C2 may represent a motion vector of a sample of(xc−1, yc+S) coordinates, C3 may represent a motion vector of a sampleof (xc, yc+S) coordinates, and C4 may represent a motion vector of asample of (xc−1, yc+S−1) coordinates. In this case, the decoding devicemay further use at least one of the motion vectors C2, C3, and C4 as aprediction candidate of v2. That is, the decoding device may furtherinclude at least one of the sample of the (xc−1, yc+S) coordinates, thesample of the (xc, yc+S) coordinates, and the sample of the (xc−1,vc+S−1) coordinates in the neighboring sample group 2.

Also, the decoding device may configure the prediction candidates forthe motion vectors of the CPs of the current block by limiting thenumber of prediction candidates to a certain number. In the case of themotion vector v0 of CP0, the decoding device may use two pieces ofmotion information, among pieces of motion information of theneighboring blocks (or neighboring samples), as prediction candidates,and the two pieces of motion information may be represented by A0 andA1. in case where a width and a height of the current block are S/2 andS, respectively, and the coordinates of the top-left sample position ofthe current block is (xp, yp), A0 may represent a motion vector of asample of (xp−1, yp−1) coordinates and A1 may represent a motion vectorof a sample of (xp, yp−1) coordinates. In this case, the decoding devicemay use A0 and A1 as prediction candidates of v0. That is, the decodingdevice may include the sample of the (xp−1, yp−1) coordinates and thesample of the (xp, yp−1) coordinates in the neighboring sample group 0,and availability of the sample of the (xp−1, yp−1) coordinates and thesample of the (xp, yp−1) coordinates may be sequentially determinedaccording to first predefined priority order.

In the case of the motion vector v1 of CP1, the decoding device may usetwo pieces of motion information, among pieces of motion information ofthe neighboring blocks neighboring samples), as prediction candidates,and the two pieces of motion information may be represented by B0 andB1. In case where a width and a height of the current block are S/2 andS, respectively, and the coordinates of the top-left sample position ofthe current block is (xp, yp), B0 may represent a motion vector of asample of (xp+S/2, yp−1) coordinates and B1 may represent a motionvector of a sample of (xp+S/2−1, yp−1) coordinates. In this case, thedecoding device may use B0 and B1 as prediction candidates of v1. Thatis, the decoding device may include the sample of the (xp+S/2, yp−1)coordinates and the sample of the (xp+S/2−1, yp−1) coordinates in theneighboring sample group 1, and availability of the sample of the(xp+S/2, yp−1) coordinates and the sample of the (xp+S/2−1, yp−1)coordinates may be sequentially determined according to secondpredefined priority order.

Also, in the case of the motion vector v2 of CP2, the decoding devicemay use two pieces of motion information, among pieces of motioninformation of the neighboring blocks (or neighboring samples), asprediction candidates, and the two pieces of motion information may berepresented by C0 and C1. In case where a width and a height of thecurrent block are S/2 and S, respectively, and the coordinates of thetop-left sample position of the current block is (xp, yp), C0 mayrepresent a motion vector of a sample of (xp−1, yp+S) coordinates and C1may represent a motion vector of a sample of (xp−1, yp+S−1) coordinates.In this case, the decoding device may use C0 and C1 as predictioncandidates of v2. That is, the decoding device may include the sample ofthe (xp−1, yp+S) coordinates and the sample of the (xp−1, yp+S−1)coordinates in the neighboring sample group 2, and availability of thesample of the (xp−1, yp+S/2) coordinates and. the sample of the (xp−1,yp+S/2−1) coordinates may be sequentially determined according to thirdpredefined priority order.

In another example, in case where the current block is a PU to which thepartitioning type nL×2N is applied, for example, in the case of themotion vector v0 of CP0, the decoding device may use three pieces ofmotion information, among pieces of motion information of neighboringblocks (or neighboring samples), as prediction candidates, and the threepieces of motion information may be represented by A0, A1, and A2,respectively. In case where a width and a height of the current blockare W and H, respectively, and coordinates of a top-left sample positionof the current block is (xp, yp), A0 may represent a motion vector of asample of (xp−1, yp−1) coordinates, A1 may represent a motion vector ofa sample of (xp, yp−1) coordinates, and A2 may represent a motion vectorof a sample of (xp−1, yp) coordinates. In this case, the decoding devicemay use at least one of the motion vectors A0, A1 and A2 as a predictioncandidate of v0. That is, the decoding device may derive the motionvector v0 regarding CP0 based on the neighboring sample group 0including at least one of the sample of the (xp−1, yp−1) coordinates,the sample of the (xp, yp−1) coordinates, and the sample of the (xp−1,yp) coordinates.

Also, in the case of the motion vector v1 of CP1, the decoding devicemay use two pieces of motion information, among pieces of motioninformation of neighboring blocks (or neighboring samples), asprediction candidates, and the two pieces of motion information may berepresented by B0 and B1. In case where a width and a height of thecurrent block are W and H, respectively, and coordinates of a top-leftsample position of the current block is (xp, yp), B0 may represent amotion vector of a sample of (xp+W, yp−1) coordinates and B1 mayrepresent a motion vector of a sample of (xp+W−1, yp−1) coordinates. Inthis case, the decoding device may use at least one of the motionvectors B0 and B1 as a prediction candidate of v1. That is, the decodingdevice may derive the motion vector v1 regarding CP1 based on theneighboring sample group 1 including the sample of the (xp+W, yp−1)coordinates and the sample of the (xp+W−1, yp−1) coordinates.

Also, in the case of the motion vector v2 of CP2, the decoding devicemay use two pieces of motion information, among pieces of motioninformation of neighboring blocks (or neighboring samples), asprediction candidates, and the two pieces of motion information may berepresented by C0 and C1. In case where a width and a height of thecurrent block are W and H, respectively, and coordinates of a top-leftsample position of the current block is (xp, yp), C0 may represent amotion vector of a sample of (xp−1, yp+H) coordinates and C1 mayrepresent a motion vector of a sample of (xp−1, yp+H−1) coordinates. Inthis case, the decoding device may use at least one of the motionvectors C0 and C1 as a prediction candidate of v2. That is, the decodingdevice may derive the: motion vector v2 regarding CP2 based on theneighboring sample group 2 including the sample of the (xp−1, yp+H)coordinates and the sample of the (xp−1, yp+H−1) coordinates.

Also, in case where a partition ID of the current block is 1, thedecoding device may further include samples of neighboring blocks of thecurrent CU as prediction candidates for the motion vector v0 of CP0 andthe motion vector v2 of CP2. For example, in the case of the motionvector v0 of CP0, the decoding device may further include motioninformation of neighboring blocks (i.e., neighboring samples) as aprediction candidate. In detail, the decoding device may further use atleast one of two pieces of motion information of neighboring samples asa prediction candidate, and the two pieces of motion information may berepresented by A3 and A4, respectively. In case where a width and aheight of the CU including the current block are H and coordinates ofthe top-left sample position of the CU is (xc, yc), A3 may represent amotion vector of a sample of (xc−1, yc−1) coordinates and A4 mayrepresent a motion vector of a sample of (xc−1, yc) coordinates. In thiscase, the decoding device may further use at least one of the motionvectors A3 and A4 as a prediction candidate of v0. That is, the decodingdevice may further include at least one of the sample of the (xc−1,yc−1) coordinates, the sample of the (xc−1, yc) coordinates, and thesample of the (xc, yc−1) coordinates in the neighboring sample group 0.

Also, in the case of the motion vector v2 of CP2, the decoding devicemay further include motion information of neighboring blocks (i.e.,neighboring samples) as a prediction candidate. In detail, the decodingdevice may further use at least one of two pieces of motion informationof neighboring samples as a prediction candidate, and the two pieces ofmotion information may be represented by C2 and C3, respectively. Incase where a width and a height of the CU including the current blockare H and coordinates of the top-left sample position of the CU is (xc,yc), C2 may represent a motion vector of a sample of (xc−1, yc+H)coordinates and C3 may represent a motion vector of a sample of (xc−1,yc+H−1) coordinates. In this case, the decoding device may further useat least one of the motion vectors C2 and. C3 as a prediction candidateof v2. That is, the decoding device may further include at least one ofthe sample of the (xc−1, yc+H) coordinates and the sample of the (xc−1,yc+H−1) coordinates in the neighboring sample group 2.

In another example, in case where the current block is a PU to which thepartitioning type nR×2N is applied, for example, in the case of themotion vector v0 of CP0, the decoding device may use three pieces ofmotion information, among pieces of motion information of neighboringblocks (or neighboring samples), as prediction candidates, and the threepieces of motion information may be represented by A0, A1, and A2,respectively. In case where a width and a height of the current blockare W and H, respectively, and coordinates of a top-left sample positionof the current block is (xp, vp), A0 may represent a motion vector of asample of (xp−1, yp−1) coordinates, A1 may represent a motion vector ofa sample of (xp, yp−1) coordinates, and A2 may represent a motion vectorof a sample of (xp−1, vp) coordinates. In this case, the decoding devicemay use at least one of the motion vectors A0, A1 and A2 as a predictioncandidate of v0. That is, the decoding device may derive the motionvector v0 regarding CP0 based on the neighboring sample group 0including at least one of the sample of the (xp−1, yp−1) coordinates,the sample of the (xp, yp−1) coordinates, and the sample of the (xp−1,yp) coordinates.

Also, in the case of the motion vector v1 of CP1, the decoding devicemay use two pieces of motion information, among pieces of motioninformation of neighboring blocks (or neighboring samples), asprediction candidates, and the two pieces of motion information may berepresented by B0 and B1. In case where a width and a height of thecurrent block are W and H, respectively, and coordinates of a top-leftsample position of the current block is (xp, yp), B0 may represent amotion vector of a sample of (xp+W, yp−1) coordinates and B1 mayrepresent a motion vector of a sample of (xp+W−1, yp−1) coordinates. Inthis case, the decoding device may use at least one of the motionvectors B0 and B1 as a prediction candidate of v1. That is, the decodingdevice may derive the motion vector v1 regarding CP1 based on theneighboring sample group 1 including the sample of the (xp+W, yp−1)coordinates and the sample of the (xp+W−1, yp−1) coordinates,

Also, in the case of the motion vector v2 of CP2, the decoding devicemay use two pieces of motion information, among pieces of motioninformation of neighboring blocks (or neighboring samples), asprediction candidates, and the two pieces of motion information may berepresented by C0 and C1. In case where a width and a height of thecurrent block are W and H, respectively, and coordinates of a top-leftsample position of the current block is (xp, yp), C0 may represent amotion vector of a sample of (xp−1, yp+H) coordinates and C1 mayrepresent a motion vector of a sample of (xp−1, yp+H−1) coordinates. Inthis case, the decoding device may use at least one of the motionvectors C0 and C1 as a prediction candidate of v2. That is, the decodingdevice may derive the motion vector v2 regarding CP2 based on theneighboring sample group 2 including the sample of the (xp−1, yp+H)coordinates and the sample of the (xp−1, yp+H−1) coordinates.

Also, in case where a partition ID of the current block is 1, thedecoding device may further include samples of neighboring blocks of thecurrent CU as prediction candidates for the motion vector v0 of CP0 andthe motion vector v2 of CP2. For example, in the case of the motionvector v0 of CP0, the decoding device may further include motioninformation of neighboring blocks (i.e.. neighboring samples) as aprediction candidate. In detail, the decoding device may further use atleast one of three pieces of motion information of neighboring samplesas a prediction candidate, and the three pieces of motion informationmay be represented by A3, A4, and A5, respectively. In case where awidth and a height of the CU including the current block are H andcoordinates of the top-left sample position of the CU is (xc, yc), A3may represent a motion vector of a sample of (xc−1, yc−1) coordinates,A4 may represent a motion vector of a sample of (xc, yc−1) coordinates,and A5 may represent a motion vector of a sample of (xc−1, yc)coordinates. In this case, the decoding device may further use at leastone of the motion vectors A3, A4, and A5 as a prediction candidate ofv0. That is, the decoding device may further include at least one of thesample of the (xc−1, yc−1) coordinates, the sample of the (xc−1, yc)coordinates, and the sample of the (xc, yc−1) coordinates in theneighboring sample group 0.

Also, in the case of the motion vector v2 of CP2, the decoding devicemay further include motion information of neighboring blocks (i.e.,neighboring samples) as a prediction candidate. In detail, the decodingdevice may further use at least one of three pieces of motioninformation of neighboring samples as a prediction candidate, and thethree pieces of motion information may be represented by C2, C3, and C4,respectively. In case where a width and a height of the CU including lecurrent block are H and coordinates of the top-left sample position ofthe CU is (xc, yc), C2 may represent a motion vector of a sample of(xc−1, yc+H) coordinates, C3 may represent a motion vector of a sampleof (xc, yc+H) coordinates, and C4 may represent a motion vector of asample of (xc−1, yc+H) coordinates. In this case, thedecoding device mayfurther use at least one of the motion vectors C2, C3, and C4 as aprediction candidate of v2. That is, the decoding device may furtherinclude at least one of the sample of the (xc−1, yc+H) coordinates, thesample of the (xc, yc+H) coordinates, and the sample of the (xc-I,yc+H−1) coordinates in the neighboring sample group 2.

In another example, in case where the current block is a PU to which thepartitioning type 2N×nU is applied, for example, in the case of themotion vector v0 of CP0, the decoding device may use three pieces ofmotion information, among pieces of motion information of neighboringblocks (or neighboring samples), as prediction candidates, and the threepieces of motion information may be represented by A0, A1, and A2,respectively. In case where a width and a height of the current blockare W and H, respectively, and coordinates of a top-left sample positionof the current block is (xp, yp), A0 may represent a motion vector of asample of (xp−1, yp−1) coordinates, A1 may represent a motion vector ofa sample of (xp, yp−1) coordinates, and A2 may represent a motion vectorof a sample of (xp−1, yp) coordinates. In this case, the decoding devicemay use at least one of the motion vectors A0, A1 and A2 as a predictioncandidate of v0. That is, the decoding device may derive the motionvector v0 regarding CP0 based on the neighboring sample group 0including at least one of the sample of the (xp−1, yp−1) coordinates,the sample of the (xp, yp−1) coordinates, and the sample of the (xp−1,yp) coordinates.

Also, in the case of the motion vector v1 of CP1, the decoding devicemay use two pieces of motion information, among pieces of motioninformation of neighboring blocks (or neighboring samples), asprediction candidates, and the two pieces of motion information may berepresented by B0 and B1. In case wherea width and a height of thecurrent block are W and H, respectively, and coordinates of a top-leftsample position of the current block is (xp, yp), B0 may represent amotion vector of a sample of (xp+W, yp−1) coordinates and B1 mayrepresent a motion vector of a sample of (xp+W−1, yp−1) coordinates. Inthis case, the decoding device may use at least one of the motionvectors B0 and B1 as a prediction candidate of v1. That is, the decodingdevice may derive the motion vector v1 regarding CP1 based on theneighboring sample group 1 including at least one of the sample of the(xp+W, yp−1) coordinates and the sample of the (xp+W−1, yp−1)coordinates.

Also, in the case of the motion vector v2 of CP2, the decoding devicemay use two pieces of motion information, among pieces of motioninformation of neighboring blocks (or neighboring samples), asprediction candidates, and the two pieces of motion information may berepresented by C0 and C1. In case where a width and a height of thecurrent block are W and H, respectively, and coordinates of a top-leftsample position of the current block is (xp, yp), C0 may represent amotion vector of a sample of (xp−1, yp+H) coordinates and C1 mayrepresent a motion vector of a sample of (xp−1, yp+H−1) coordinates. Inthis case, the decoding device may use at least one of the motionvectors C0 and C1 as a prediction candidate of v2. That is, the decodingdevice may derive the motion vector v2 regarding CP2 based on theneighboring sample group 2 including at least one of the sample of the(xp−1, yp+H) coordinates and the sample of the (xp−1, coordinates.

Also, in case where a partition ID of the current block is 1, thedecoding device may further include samples of neighboring blocks of thecurrent CU as prediction candidates for the motion vector v0 of CP0 andthe motion vector v1 of CP1 For example, in the case of the motionvector v0 of CP0, the decoding device may further include motioninformation of neighboring blocks (i.e., neighboring samples) as aprediction candidate. In detail, the decoding device may further use atleast one of two pieces of motion information of neighboring samples asa prediction candidate, and the two pieces of motion information may berepresented by A3 and A4, respectively. In case where a width and aheight of the CU including the current block are W and coordinates ofthe top-left sample position of the CU is (xc, yc), A3 may represent amotion vector of a sample of (xc−1, yc−1) coordinates and A4 mayrepresent a motion vector of a sample of (xc, yc−1) coordinates. In thiscase, the decoding device may further use at least one of the motionvectors A3 and 44 as a prediction candidate of v0. That is, the decodingdevice may further include at least one of the sample of the (xc−1,yc−1) coordinates and the sample of the (xc, yc−1) coordinates in theneighboring sample group 0.

Also, in the case of the motion vector v1 of CP1, the decoding devicemay further include motion information of neighboring blocks (i.e.,neighboring samples) as a prediction candidate. In detail, the decodingdevice may further use at least one of two pieces of motion informationof neighboring samples as a prediction candidate, and the two pieces ofmotion information may be represented by B2 and B3, respectively. Incase where a width and a height of the CU including the current blockare W and coordinates of the top-left sample position of the CU is (xc,vc), B2 may represent a motion vector of a sample of (xc+W, yc−1)coordinates and B3 may represent a motion vector of a sample of (xc+W−1,yc−1) coordinates. In this case, the decoding device may further use atleast one of the motion vectors B2 and B3 as a prediction candidate ofv1. That is, the decoding device may further include at least one of thesample of the (xc+W, yc−1) coordinates and the sample of the (xc+W−1,yc−1) coordinates in the neighboring sample group 1.

In another example, in case where the current block is a PU to which thepartitioning type 2N×nD is applied, for example, in the case of themotion vector v0 of CP0, the decoding device may use three pieces ofmotion information, among pieces of motion information of neighboringblocks (or neighboring samples), as prediction candidates, and the threepieces of motion information may be represented by A0, A1, and A2,respectively. In case where a width and a height of the current blockare W and H, respectively, and coordinates of a top-left sample positionof the current block is (xp, yp), A0 may represent a motion vector of asample of (xp−1, yp−1) coordinates, A1 may represent a motion vector ofa sample of (xp, yp−1) coordinates, and A2 may represent a motion vectorof a sample of (xp−1, yp) coordinates. In this case, the decoding devicemay use at least one of the motion vectors A0, A1 and A2 as a predictioncandidate of v0. That is, the decoding device may derive the motionvector v0 regarding CP0 based on the neighboring sample group 0including at least one of the sample of the (xp−1, yp−1) coordinates,the sample of the (xp, yp−1) coordinates, and the sample of the (xp−1,yp) coordinates.

Also, in the case of the motion vector v1 of CP1, the decoding devicemay use two pieces of motion information, among pieces of motioninformation of neighboring blocks (or neighboring samples), asprediction candidates, and the two pieces of motion information may berepresented by B0 and B1. In case where a width and a height of thecurrent block are W and H, respectively, and coordinates of a top-leftsample position of the current block is (xp, yp), B0 may represent amotion vector of a sample of (xp+W, yp−1) coordinates and B1 mayrepresent a motion vector of a sample of (xp+W−1, yp−1) coordinates. Inthis case, the decoding device may use at least one of the motionvectors B0 and B1 as a prediction candidate of v1. That is, the decodingdevice may derive the motion vector v1 regarding CP1 based on theneighboring sample group 1 including at least one of the sample of the(xp+W, yp−1) coordinates and the sample of the (xp+W−1, yp−1)coordinates.

Also, in the case of the motion vector v2 of CP2, the decoding devicemay use two pieces of motion information, among pieces of motioninformation of neighboring blocks (or neighboring samples), asprediction candidates, and the two pieces of motion information may berepresented by C0 and C1. In case where a width and a height of thecurrent block are W and H, respectively, and coordinates of a top-leftsample position of the current block is (xp, yp), C0 may represent amotion vector of a sample of (xp−1, yp+H) coordinates and C1 mayrepresent a motion vector of a sample of (xp−1, yp+H−1) coordinates. Inthis case, the decoding device may use at least one of the motionvectors C0 and C1 as a prediction candidate of v2. That is, the decodingdevice may derive the motion vector v2 regarding CP2 based on theneighboring sample group 2 including at least one of the sample of the(xp−1, yp+H) coordinates and the sample of the (xp−1, yp+H−1)coordinates.

Also, in case where a partition ID of the current block is 1, thedecoding device may further include samples of neighboring blocks of thecurrent CU as prediction candidates for the motion vector v0 of CP0 andthe motion vector v1 of CP1. For example, in the case of the motionvector v0 of CP0, the decoding device may further include motioninformation of neighboring blocks (i.e., neighboring samples) as aprediction candidate. In detail, the decoding device may further use atleast one of three pieces of motion information of neighboring samplesas a prediction candidate, and the three pieces of motion informationmay be represented by A3, A4, and A5, respectively. In case where awidth and a height of the CU including the current block are W andcoordinates of the top-left sample position of the CU is (xc, yc), A3may represent a motion vector of a sample of (xc−1, yc) coordinates, A4may represent a motion vector of a sample of (xc−1, yc−1) coordinates,and A5 may represent a motion vector of a sample of (xc, yc−1)coordinates. In this case, the decoding device may further use at leastone of the motion vectors A3, A4, and A5 as a prediction candidate ofv0. That is, the decoding device may further include at least one of thesample of the xc−1, yc−1) coordinates, the sample of the (xc−1, yecoordinates, and the sample of the (xc, yc−1) coordinates in theneighboring sample group 0.

Also, in the case of the motion vector v1 of CP1, the decoding devicemay further include motion information of neighboring blocks (i.e.,neighboring samples) as a prediction candidate. In detail, the decodingdevice may further use at least one of three pieces of motioninformation of neighboring samples as a prediction candidate, and thethree pieces of motion information may be represented by B2, B3, and B4,respectively. In case where a width and a height of the CU including thecurrent block are W and coordinates of the top-left sample position ofthe CU is (xc, yc), B2 may represent a motion vector of a sample of(xc+W, yc) coordinates, B3 may represent a motion vector of a sample of(xc+W yc−1) candidates, and B4 may represent a motion vector of a sampleof (xc+W−1, yc−1) coordinates. In this case, the decoding device mayfurther use at least one of the motion vectors B2, B3, and B4 as aprediction candidate of v1. That is, the decoding device may furtherinclude at least one of the sample of the (xc+W, yc) coordinates, thesample of the (xc+W, yc−1) coordinates, and the sample of the (xc+W−1,yc−1) coordinates in the neighboring sample group 1.

In another example, the decoding device may use the same predictioncandidates of PUs included in the CU may use the same predictioncandidates of the PUs in the CU as prediction candidates for the motionvectors of the CPs, regardless of partition ID. For example, in the caseof the motion vector v0 of CP0 of the current block., the decodingdevice may use three pieces of motion information, among pieces ofmotion information of neighboring blocks (i.e., neighboring blocks orneighboring samples of the current CU), as prediction candidates, andthe three pieces of motion information may be represented by A0, A1, andA2, respectively. In case where a width and a height of the CU are W andH, respectively, and coordinates of the top-left sample position of theCU is (xc, yc), A0 may represent a motion vector of a sample of (xc−1,yc−1) coordinates, A1 may represent a motion vector of a sample of (xc,yc−1) coordinates, and A2 may represent a. motion vector of a sample of(xc−1, yc) coordinates. In this case, the decoding device may use atleast one of the motion vectors A0, A1 and A2 as a prediction candidateof v0.

Also, in the case of the motion vector v1 of CPI of the current block,the decoding device may use two pieces of motion information, amongpieces of motion information of neighboring blocks (or neighboringsamples), as prediction candidates, and the two pieces of motioninformation may be represented by B0 and B1. In case where a width and aheight of the CU are W and coordinates of the top-left sample positionof the CU is (xc, yc), B0 may represent a motion vector of a sample of(xc+W, yc−1) coordinates and B1 may represent a motion vector of asample of (xc+W−1, yc−1) coordinates. In this case, the decoding devicemay use at least one of the motion vectors B0 and B1 as a predictioncandidate of v1.

Also, in the case of the motion vector v2 of CP2 of the current block,the decoding device may use two pieces of motion information, amongpieces of the motion information of the neighboring blocks (orneighboring samples), as prediction candidates, and the two pieces ofmotion information may be represented by C0 and C1, respectively. Incase where a width and a height of the CU are W and coordinates of thetop-left sample position of the CU is (xc, yc), C0 may represent amotion vector of a sample of (xc−1, yc+H) coordinates and C1 mayrepresent a motion vector of a sample of (xc−1, yc+H−1) coordinates. Inthis case, the decoding device may use at least one of the motionvectors C0 and C1 as a prediction candidate of v2.

In another example, as a method of configuring a prediction candidatefor motion vectors of CPs of a PU to which the nL×2N, nR×2N, 2N×nU, or2N×nD partitioning type is applied, prediction candidates may be limitedto a predetermined number so as to be configured.

In another example, in case where the current block is a PU to which thepartitioning type nL×2N, nR×2N, 2N×nU, or 2N×nD is applied, the decodingdevice may configure the prediction candidates of each CP by limitingthe number thereof into two. For example, in the case of the motionvector v0 of CP0, the decoding device may use two pieces of motioninformation, among pieces of motion information of the neighboringblocks (or neighboring samples), as prediction candidates, and the twopieces of motion information may be represented by A0 and A1. In casewhere a width and a height of the current block are W and H,respectively, and the coordinates of the top-left sample position of thecurrent block is (xp, yp), A0 may represent a motion vector of a sampleof (xp−1, yp−1) coordinates and A1 may represent a motion vector of asample of (xp, yp−1) coordinates. In this case, the decoding device mayuse A0 and A1 as prediction candidates of v0. That is, the decodingdevice may include the sample of the (xp−1, yp−1) coordinates and thesample of the (xp, yp−1) coordinates in the neighboring sample group 0,and availability of the sample of the (xp−1, yp−1) coordinates and thesample of the (xp, yp−1) coordinates may be sequentially determinedaccording to first predefined priority order.

Also, in the case of the motion vector v1 of CP1, the decoding devicemay use two pieces of motion information, among pieces of motioninformation of the neighboring blocks (or neighboring samples), asprediction candidates, and the two pieces of motion information may berepresented by B0 and B1. In case where a width and a height of thecurrent block are W and H, respectively, and the coordinates of thetop-left sample position of the current block is (xp, yp), B0 mayrepresent a motion vector of a sample of (xp+W, yp−1) coordinates and B1may represent a motion vector of a sample of (xp+W, yp−1) coordinates.In this case, the decoding device may use B0 and B1 as predictioncandidates of v1. That is, the decoding device may include the sample ofthe (xp+W, yp−1) coordinates and the sample of the (xp+W−1, yp−1)coordinates in the neighboring sample group I, and availability of thesample of the (xp+W, yp−1) coordinates and the sample of the (xp+W−1,yp−1) coordinates may be sequentially determined according to secondpredefined priority order.

Also, in the case of the motion vector v2 of CP2, the decoding devicemay use two pieces of motion information, among pieces of motioninformation of the neighboring blocks (or neighboring samples), asprediction candidates, and the two pieces of motion information may berepresented by C0 and C1. In case where a width and a height of thecurrent block are W and H, respectively, and the coordinates of thetop-left sample position of the current block is (xp, yp), C0 mayrepresent a motion vector of a sample of (xp−1, yp+H) coordinates and C1may represent a motion vector of a sample of (xp−1, yp+H−1) coordinates.In this case, the decoding device may use C0 and C1 as predictioncandidates of v2. That is, the decoding device may include the sample ofthe (xp−1, yp+H) coordinates and the sample of the (xp−1, yp+H)coordinates in the neighboring sample group 2, and availability of thesample of the (xp−1, yp+H) coordinates and the sample of the (xp−1,yp+H−1) coordinates may be sequentially determined according to thirdpredefined priority order.

In addition, the decoding device may derive the motion vectors of theCPs of the current PU based on the motion vectors derived in theprevious decoding process, without receiving additional motioninformation.

For example, in the case of CP0, in case where an uppermost block, amongleft neighboring blocks adjacent to a left boundary of the currentblock, is decoded based on the affine motion model, a motion vector ofCP0 of the current block may be derived based on a motion vector of CP1of the corresponding block. Also, in case where a leftmost block, amongupper neighboring blocks adjacent to an upper boundary of the currentblock, is decoded based on the affine motion model, a motion vector ofCP0 of the current block may be derived based on a motion vector of CP2of the corresponding block. Also, in case where an upper leftneighboring block of the current block is decoded based on the affinemotion model, a motion vector of CP0 of the current block may be derivedbased on a motion vector of a lower right neighboring sample of thecorresponding block derived based on the CPs of the corresponding block.In this case, the motion vector of the lower right neighboring sample ofthe corresponding block may be derived based on the CPs of thecorresponding block based on Equations 2 to 5 described above.

For example, in the case of CP1, in case where an upper rightneighboring block of the current block is decoded based on the affinemotion model, a motion vector of CP1 of the current block may be derivedbased on a motion vector of CP2 of the corresponding block. In casewhere a rightmost block of the upper neighboring blocks adjacent to theupper boundary of the current block is decoded based on the affinemotion model, a motion vector of CP1 of the current block may be derivedbased on a motion vector of a lower right neighboring sample of thecorresponding block derived based on the CPs of the block. In this case,the motion vector of the lower right neighboring samples of thecorresponding block may be derived based on the CPs of the correspondingblock based on Equations 2 to 5 described above.

For example, in the case of CP2, in case where a lower left neighboringblock of the current block is decoded based on the affine motion model,a motion vector of CP2 of the current block may be derived based on amotion vector of CP1 of the corresponding block. Also, in case where alowermost block of left neighboring blocks adjacent to a left boundaryof the current block is decoded based on the affine motion model, amotion vector of CP2 of the current block may be derived based on amotion vector of a lower right neighboring sample of the correspondingblock derived based on the CPs of the current block. In this case, themotion vector of the lower right neighboring sample of the correspondingblock may be derived based on the CPs of the corresponding block basedon Equations 2 to 5 described above.

The decoding device derives a sample unit motion vector in the currentblock based on the Obtained motion vectors (S2020). Based on the motionvector of CP0, the motion vector of CP1, and the motion vector of CP2,the decoding device may derive a sample unit motion vector according toa sample position in the current block, In this case, the decodingdevice may derive the sample unit motion vector at the sample positionin the current block based on Equations 2 to 5.

The decoding device derives a prediction sample for the current blockbased on the sample unit motion vector (S2030). The decoding device mayderive a reference region in a reference picture based on the sampleunit motion vector and generate a prediction sample of the current blockbased on the reconstructed sample in a reference region.

The decoding device may generate a reconstructed sample based on theprediction sample. If a prediction mode for the current block is not askip mode, the decoding device may acquire a residual signal from a bitstream received from the encoding device and generate a residual samplefor the current block. In this case, the decoding device may generatethe reconstructed sample based on the prediction sample and the residualsample. The decodi.ng device may generate a reconstructed picture basedon the reconstructed sample.

According to the present invention described above, more accurate sampleunit motion vectors for the current block may be derived and interprediction efficiency may significantly be increased.

Also, according to the present invention, a motion vector for samples ofa current block may be efficiently derived based on motion vectors ofcontrol points for the current block.

Also, according to the present invention, motion vectors of controlpoints for a current block may be derived based on motion vectors ofcontrol points of a previously decoded neighboring block, withoutadditionally transmitting information regarding the motion vectors ofthe control points for the current block. Accordingly, an amount of datafor the motion vectors of the control points may be eliminated orreduced, and overall coding efficiency may be improved.

In addition, according to the present invention, inter-prediction may beeffectively performed through sample unit motion vectors even in casewhere an image:of the current block is rotated, zoomed in, zoomed out,or deformed in parallelogram, as well as in case where the image of thecurrent block is plane-shifted. Accordingly, an amount of data for theresidual signal for the current block may be eliminated or reduced andoverall coding efficiency may be improved.

In the above-described embodiments, methods are described on the basisof a flowchart using a series of steps or blocks, but the presentinvention is not limited to the sequence of steps. Some steps may occursimultaneously or in a different sequence than the steps describedabove. Further, those skilled in the art will understand that the stepsillustrated in the sequence diagram are not exclusive, that other stepsmay be included, or that one or more steps in the flowchart may bedeleted without affecting the scope of the present invention.

The method according to the present invention described above may beimplemented in software. The encoding device and/or decoding deviceaccording to the present invention may be included in a device thatperforms image processing, for example, for a TV, a computer, a smartphone, a set-top box, or a display device.

When the embodiments of the present invention are implemented insoftware, the above-described method may be implemented by modules(processes, functions, and so on) that perform the functions describedabove. Such modules may be stored in memory and executed by a processor.The memory may be internal or external to the processor, and the memorymay be coupled to the processor using various well known means. Theprocessor may comprise an application-specific integrated circuit(ASIC), other chipsets, a logic circuit and/or a data processing device.The memory may include a ROM (read-only memory), a RAM (random accessmemory), a flash memory, a memory card, a storage medium, and/or otherstorage device.

What is claimed is:
 1. A video decoding method performed by a decodingdevice, the video decoding method comprising: deriving motion vectorsfor control points (CPs) for a current block; deriving a motion vectorfor the current block based on the obtained motion vectors for the CPs;performing a prediction for the current block based on the motion vectorfor the current block; and generating a reconstructed block for thecurrent block based on a result of the prediction for the current block,wherein the CPs includes a first CP, a second CP and a third CP, whereinthe first CP is for a top-left corner of the current block, the secondCP is for a top-right corner of the current block and the third CP isfor bottom-left corner of the current block, wherein the motion vectorsfor the CPs include a first motion vector for the first CP, a secondmotion vector for the second CP and a third motion vector for the thirdCP, wherein the first motion vector is derived based on afirstly-checked available block according to a first predefined priorityorder in a first block group, wherein the first block group comprises atop-left corner neighboring block of the current block, a first topneighboring block which is leftmost block among blocks adjacent to anupper side of the current block and a first left neighboring block whichis an uppermost block among blocks adjacent to a left side of thecurrent block, wherein the second motion vector is derived based on afirstly-checked available block according to a second predefinedpriority order in a second block group, wherein the second block groupcomprises a top-right corner neighboring block of the current block anda second top neighboring block which is a rightmost block among theblocks adjacent to the upper side of the current block, wherein thethird motion vector is derived based on a firstly-checked availableblock according to a third predefined priority order in a third blockgroup, and wherein the third block group comprises a bottom-left cornerneighboring block of the current block and a second left neighboringblock which is a lowermost block amonghe blocks adjacent to the leftside of the current block.
 2. The video decoding method of claim 1,wherein the motion vector related to a sample position for the currentblock is derived based on the following equations,Vx=(Vx1−Vx0)*x/W+(v1×2−Vx0)*y/H+Vx0, Vy=(Vy1−Vy0)*x/W+(Vy2−Vy0)*y/H+Vy0,and wherein the Vx represents a x component of the motion vector relatedto the sample position at a coordinate of (x, y), the Vy represents a ycomponent of the motion vector related to the sample position at thecoordinate of (x, y), the Vx0 represents a x component of the firstmotion vector for the first CP, the Vy0 represents a y component of thefirst motion vector for the second CP, the Vx1 represents a x componentof the second motion vector for the second CP, the Vy1 represents a ycomponent of the second motion vector for the second CP, the Vx2represents a x component of the third motion vector for the third CP,the Vvz, represents a y component of the third motion vector for thethird CP, and W and H are a width and a height of the current blockrespectively.
 3. The video decoding method of claim wherein the top-leftcorner neighboring block is located o.ri the coordinate of (xc−1, yc−1),the first top neighboring block is located on the coordinate of (xc,yc−1), and the first left neighboring block is located on the coordinateof (xc−1, yc), the top-right corner neighboring block is located on thecoordinate of (xc+W, yc−1) and the second top neighboring block islocated on the coordinate of (xc+W−1, yc−1), and the bottom-left cornerneighboring block is located on the coordinate of (xc−1, yc+H) and thesecond left neighboring block is located on the coordinate of (xc−1,yc+H−1), and wherein (xc, yc) is a top-left sample position of thecurrent block, and W and H are a width and a height of the current blockrespectively.
 4. The video decoding method of claim 1, wherein the thirdmotion vector for the third CP is derived from the third block groupcomprising the bottom-left corner neighboring block and the second left,neighboring block based on a third predefined priority order, whereinthe first predefined priority order is from the top-left cornerneighboring block to the first top neighboring block to the first leftneighboring block, wherein the second predefined priority order is fromthe top-right corner neighboring block to the second top neighboringblock, and wherein the third predefined priority order is from thebottom-left corner neighboring bock to the second left neighboringblock.
 5. The video decoding method of claim 1, wherein the second CP islocated on a coordinate of (xc+W, yc) and the third CP is located on acoordinate of (xc, yc+W/2), and wherein (xc, yc) is a top-left sampleposition of the current block, and W and H are a width and a height ofthe current block respectively.
 6. The video decoding method of claim 1,wherein: the motion vector related to a sample position for the currentblock is derived based on the following equations,Vx=(Vx1−Vx0)*x/W+(Vx2−Vx0)*y/(W/2)+Vx0, wherein the Vx represents a xcomponent of the motion vector related to the sample position at acoordinate of (x, y), the Vy represents a y component of the motionvector related to the sample position at the coordinate of (x, y), theVx0 represents a x component of the first motion vector for the firstCP, the Vy0 represents a y component of the first motion vector for thefirst CP, the Vx1 represents a x component of the second motion vectorfor the second CP, the Vy1 represents a y component of the second motionvector 1 for the second CP, the Vx2 represents a x component of thethird motion vector for the third CP, the Vy2 represents a y componentof the third motion vector for the third CP, and W and H are a width anda height of the current block respectively.
 7. The video decoding methodof claim 1, wherein: the top-left corner neighboring block is located onthe coordinate of (xc−1, yc−1), the first top neighboring block islocated on the coordinate of (xc, yc−1), and the first left neighboringblock is located on the coordinate of (xc−1, yc), the top-right cornerneighboring block is located on the coordinate of (xc+W, yc−1) and thesecond top neighboring block is located on the coordinate of (xc+W−1,yc−1), and the bottom-left corner neighboring block is located on acoordinate of (xc−1, yc+W/2) and the second left neighboring block islocated on a coordinate of (xc−1, yc+W/2−1).
 8. A video encoding methodperformed by an encoding device, the video encoding method including:deriving motion vectors for control points (CPs) for a current block;deriving a motion vector for the current block based on the obtainedmotion vectors for the CPs; performing a prediction for the currentblock based on the motion vector for the current block; and encodingvideo information including information on the prediction for thecurrent block, wherein the CPs includes a first CP, a second CP and athird CP, wherein the first CP is for a top-left corner of the currentblock, the second CP is for a top-right corner of the current block andthe third CP is for bottom-left corner of the current block, wherein themotion vectors for the CPs include a first motion vector for the firstCP, a second motion vector for the second CP and a third motion vectorfor the third CP, wherein the first motion vector is derived based on afirstly-checked available block according to a first predefined priorityorder in a first block group, wherein the first block group comprises atop-left corner neighboring block of the current block, a first topneighboring block which is leftmost block among blocks adjacent to anupper side of the current block and a first left neighboring block whichis an uppermost block among blocks adjacent to a left side of thecurrent block, wherein the second motion vector is derived based on afirstly-checked available block according to a second predefinedpriority order in a second block group, wherein the second block groupcomprises a top-right corner neighboring block of the current block anda second top neighboring block which is a rightmost block among theblocks adjacent to the upper side of the current block, wherein thethird motion vector is derived based on a firstly-checked availableblock according to a third predefined priority order in a third blockgroup, and wherein the third block group comprises a bottom-left cornerneighboring block of the current block and a second left neighboringblock which is a lowermost block among;the blocks adjacent to the leftside of the current block.
 9. The video encoding method of claim 8,wherein the motion vector related to a sample position for the currentblock is derived based on the following equations.Vx=(Vx1−Vx0)*x/W+(v1×2−Vx0)*y/H+Vx0, Vy=(Vy1−Vy0)*x/W+(Vy2−Vy0)*y/H+Vy0,and wherein the Vx represents a x component of the motion vector relatedto the sample position at a coordinate of (x, y), the Vy represents a ycomponent of the motion vector related to the sample position at thecoordinate of (x, y), the Vx0 represents a x component of the firstmotion vector for the first CP, the Vy0 represents a y component of thefirst motion vector for the second. CP, the Vx1 represents a x componentof the second motion vector for the second CP, the Vy1 represents a ycomponent of the second motion vector for the second CP, the Vx2represents a x component of the third motion vector for the third CP,the Vy2 represents a y component of the third motion vector for thethird CP, and W and H are a width and a height of the current blockrespectively.
 10. The video encoding method of claim 8, wherein thetop-left corner neighboring block is located on the coordinate of (xc−1,yc−1), the first top neighboring block is located on the coordinate of(xc, yc−1), and the first left neighboring block is located on thecoordinate of (xc−1, yc), the top-right corner neighboring block islocated on the coordinate of (xc+W, yc−1) and the second top neighboringblock is located on the coordinate of (xc+W−1, yc−1), and thebottom-left corner neighboring block is located on the coordinate of(xc−1, yc+H) and the second left neighboring block is located on thecoordinate of (xc−1, yc+H−1).
 11. The video encoding method of claim 8,wherein the first predefined priority order is from the top-left cornerneighboring block to the first top neighboring block to the first leftneighboring block, wherein the second predefined priority order is fromthe top-right corner neighboring block to the second top neighboringblock, and wherein the third predefined priority order is from thebottom-left corner neighboring bock to the second left neighboringblock.
 12. The video encoding method of claim 8, wherein the second CPis located on a coordinate of and the third CP is located on acoordinate of (xc, yc+W/2), wherein (xc, yc) is a top-left sampleposition of the current block, and W and H are a width and a height ofthe current block respectively.
 13. The video encoding method of claim8, wherein: the motion vector related to a sample position for thecurrent block is derived based on the following equations,Vx=(Vx1−Vx0)*x/W+(Vx2−Vx0)*y/(W/2)+Vx0, wherein the Vx represents a xcomponent of the motion vector related to the sample position at acoordinate of (x, v). the Vv represents a y component of the motionvector related to the sample position at the coordinate of (x, y), theVx0 represents a x component of the first motion vector for the firstCP, the Vy0 represents a y component of the first motion vector for thefirst CP, the Vx1 represents a x component of the second motion vectorfor the second CP, the Vy1 represents a y component of the second motionvector 1 for the second CP, the Vx2 represents a x component of thethird motion vector for the third CP, the Vy2 represents a y componentof the third motion vector for the third CP, and W and H are a width anda height of the current block respectively.
 14. The video encodingmethod of claim 8, wherein: the top-left corner neighboring block islocated on the coordinate of (xc−1, yc−1), the first top neighboringblock is located on the coordinate of (xc, yc−1), and the first leftneighboring block is located on the coordinate of (xc−1, yc), thetop-right corner neighboring block is located on the coordinate of(xc+W, yc−1) and the second top neighboring block is located on thecoordinate of (xc+W−1, yc−1), and the bottom-left corner neighboringblock is located on a coordinate of (xc−1, yc+W/2) and the second leftneighboring block is located on a coordinate of (xc−1, yc+W/2−1).
 15. Anon-transitory computer-readable digital storage medium storing abitstream generated by a video encoding method, the method comprising:deriving motion vectors for control points (CPs) for a current block;deriving a motion vector for the current block based on the obtainedmotion vectors for the CPs; performing a prediction for the currentblock based on the motion vector for the current block; and encodingvideo information including information on the prediction for thecurrent block to output the bitstream, wherein the CPs includes a firstCP, a second CP and a third CP, wherein the first CP is for a top-leftcorner of the current block, the second CP is for a top-right corner ofthe current block and the third CP is for bottom-left corner of thecurrent block, wherein the motion vectors for the CPs include a firstmotion vector for the first CP, a second motion vector for the second CPand a third motion vector for the third CP, wherein the first motionvector is derived based on a firstly-checked available block accordingto a first predefined priority order in a first block group, wherein thefirst block group comprises a top-left corner neighboring block of thecurrent block, a first top neighboring block which is leftmost blockamong blocks adjacent to an upper side of the current block and a firstleft neighboring block which is an uppermost block among blocks adjacentto a left side of the current block, wherein the second motion vector isderived based on a firstly-checked available block according to a secondpredefined priority order in a second block group, wherein the secondblock group comprises a top-right corner neighboring block of thecurrent block and a second top neighboring block which is a rightmostblock among the blocks adjacent to the upper side of the current block,wherein the third motion vector is derived based on a firstly-checkedavailable block according to a third predefined priority order in athird block group, and wherein the third block group comprises abottom-left corner neighboring block of the current block and a secondleft neighboring block which is a lowermost block among the blocksadjacent to the left side of the current block.
 16. A transmissionmethod of data for a video, the method comprising: obtaining a bitstreamfor the video, wherein the bitstream is generated based on derivingmotion vectors for control points (CPs) for a current block, deriving amotion vector for the current block based on the obtained motion vectorsfor the CPs, performing a prediction for the current block based on themotion vector for the current block, and encoding video informationincluding information on the prediction for the current block; andtransmitting the data comprising the bitstream, wherein the CPs includesa first CP, a second CP and a third CP, wherein the first CP is for atop-left corner of the current block, the second CP is for a top-rightcorner of the current block and the third CP is for bottom-left cornerof the current block, wherein the motion vectors for the CPs include afirst motion vector for the first CP, a second motion vector for thesecond CP and a third motion vector for the third CP, wherein the firstmotion vector is derived based on a firstly-checked available blockaccording to a first predefined priority order in a first block group,wherein the first block group comprises a top-left coiner neighboringblock of the current block, a first top neighboring block which isleftmost block among blocks adjacent to an upper side of the currentblock and a first left neighboring block which is an uppermost blockamong blocks adjacent to a left side of the current block, wherein thesecond motion vector is derived based on a firstly-checked availableblock according to a second predefined priority order in a second blockgroup, wherein the second block group comprises a top-right cornerneighboring block of the current block and a second top neighboringblock which is a rightmost block among the blocks adjacent to the upperside of the current block, wherein the third motion vector is derivedbased on a firstly-checked available block according to a thirdpredefined priority order in a third block group, and wherein the thirdblock group comprises a bottom-left corner neighboring block of thecurrent block and a second left neighboring block which is a lowermostblock among the blocks adjacent to the left side of the current block.